Gentrification is the movement of relatively more affluent or advantaged residents into an area, perceived as altering the area's character and typically associated with a rise in property rents and prices.
'Gentrification' is a contested, often ambiguously and variously used or understood term, and is most commonly used to imply or emphasize negative effects. However, the circumstances it describes are typically complex mixtures of dynamics and effects, which may be positive or negative from the standpoint of different parties involved. Therefore, in studying phenomena of this type it may be advantageous to break it down into specific dynamics and effects: for example, displacement, decreased affordability, demographic change, or loss of social capital.
Ruth Glass' original definition, 1964
In her introduction to the book London: Aspects of Change in 1964, the urban sociologist Ruth Glass coined the term ‘gentrification’, to describe the influx of middle-class people displacing lower-class worker residents in urban neighborhoods; her example was London, and its working-class districts such as Islington.
One by one, many of the working class quarters of London have been invaded by the middle classes -- upper and lower. Shabby, modest mews and cottages -- two rooms up and two down -- have been taken over, when their leases have expired, and have become elegant, expensive residences. Larger Victorian houses, downgraded in an earlier or recent periods -- which were used as lodging houses or were otherwise in multiple occupation -- have been upgraded once again. Nowadays, many of these houses are being sub-divided into costly flats or "houselets" (in terms of the new real estate snob jargon). The current social status and value of such dwellings are frequently in inverse relation to their size, and in any case enormously inflated by comparison with previous levels in their neighbourhoods. Once this process of "gentrification" starts in a district, it goes on rapidly until all or most of the original working class occupiers are displaced, and the whole social character of the district is changed.
London: Aspects of Change was the result of work by the Centre for Urban Studies at University College London (UCL), established in 1958 and led by Ruth Glass. The Centre contributed to ‘the systematic knowledge of urban development, structure and society, and to link academic social research with social policy’.
The book brought together ten chapters by sociologists, geographers, planners, historians and health scientists to sketch a general social profile of a city that had undergone rapid contemporary change.
#DefinitionsofGentrification thread started by John Joe Schlichtman 
Sociologist J.J. Schlichtman (co-author of Gentrifier, 2017; @JJSchlichtman) created a Twitter thread on 26 Dec 2017 to post some definitions and invite others:
- GENTRIFICATION (Def. #1)The in-migration of affluent households to poorer and lower value areas of the city. [Source: Atkinson & Wulff, 2009, 4]
- GENTRIFICATION (Def. #2): The transformation of a working-class or vacant area of a city into middle-class residential and/or commercial use, [Source: Slater, 2009, 294]
- GENTRIFICATION (Def. #3): "The reinvestment of real estate capital into declining, inner-city neighborhoods to create a new residential infrastructure for middle and high-income inhabitants.”
[Source: Patch & Brenner, 2007, 1917–20]
- GENTRIFICATION (Def. #4): The reinvestment of capital at the urban center, which is designed to produce space for a more affluent class of people than currently occupies the space [Source: Smith, 2000, 294]
- GENTRIFICATION (Def. #5): A process involving a change in the pop. of land-users such that new users are of a higher SES than previous users, together with an assoc. change in the built environment through a reinvestment in fixed capital. [Clark 2005]
- GENTRIFICATION (Def. #6): The rehabilitation of working class and derelict housing and the consequent transformation of an area into a middle-class neighborhood. [Source: Smith and Williams, 1986:1]
- GENTRIFICATION (Def. #7): An econ & soc process whereby private capital (RE firms, developers) & indiv homeowners & renters reinvest in fiscally neglected n'hoods through housing rehab, loft conv, & the construction of new housing stock. [Pérez 2004]
- GENTRIFICATION (Def. #8): The process through which poor and working-class neighborhoods in the inner city are refurbished via an influx of private capital and middle-class home buyers and renters. [Smith 1996, 32]
- GENTRIFICATION (Def. #9): the movement of relatively more affluent or advantaged residents into an area, perceived as altering the area's character and typically associated with a rise in property rents and prices. [YIMBYwiki 2017].
- GENTRIFICATION (Def. #10): A process in which an influx of high-status low-income residents to a low-cost neighborhood subsequently attracts residents of higher income. [Ross “Dead End” p 87] from @BenRossTransit https://twitter.com/BenRossTransit/status/946001813848952832https://www.amazon.com/Dead-End-Suburban-American-Urbanism/dp/019026330X/
- GENTRIFICATION (Def. #11): "The replacement of lower status residents by higher status residents in a residential area" (translated from german) seems to be the common core of all definitions used in German scientific debate.
Jan Üblacker @januebl https://twitter.com/januebl/status/946012379137085441.
- GENTRIFICATION (Def. #12): a profit-driven racial & class reconfiguration of urban, working-class and communities of color that have suffered from a history of disinvestment and abandonment. [@CausaJusta1 2014].
US Centers for Disease Control and Prevention 
In the US, the Centers for Disease Control and Prevention report "Health Effects of Gentrification" [year?] defined gentrification as:
"the transformation of neighborhoods from low value to high value. This change has the potential to cause displacement of long-time residents and businesses ... when long-time or original neighborhood residents move from a gentrified area because of higher rents, mortgages, and property taxes. Gentrification is a housing, economic, and health issue that affects a community's history and culture and reduces social capital. It often shifts a neighborhood's characteristics, e.g., racial-ethnic composition and household income, by adding new stores and resources in previously run-down neighborhoods."
Causa Justa :: Just Cause
The 2014 report "Development without Displacement: Resisting Gentrification in the Bay Area." by Causa Justa::Just Cause states:
"We define gentrification as a profit-driven racial and class reconfiguration of urban, working-class and communities of color that have suffered from a history of disinvestment and abandonment. The process is characterized by declines in the number of low-income, people of color in neighborhoods that begin to cater to higher-income workers willing to pay higher rents. Gentrification is driven by private developers, landlords, businesses, and corporations, and supported by the government through policies that facilitate the process of displacement, often in the form of public subsidies. Gentrification happens in areas where commercial and residential land is cheap, relative to other areas in the city and region, and where the potential to turn a profit either through repurposing existing structures or building new ones is great."
Alex Proud - 'Shoreditchification' 
UK journalist Alex Proud coined the term Shoreditchification in 2014 to describe gentrification-like transformation of an urban area such as happened in preceding years in the Shoreditch area of London.
East Shoreditch, and adjoining Bethnal Green areas, in late 19th C. London contained some of the country's most notorious slum areas, particularly the section known as Old Nichols. Bestselling novel A Child of the Jago" by Arthur Morrison helped establish Old Nichols (also known as "the jago") as an icon of urban squalor:
the world’s first large-scale housing project was also built in London, to replace one of the capital’s most notorious slums – the Old Nichol. Nearly 6,000 individuals were crammed into the packed streets, where one child in four died before his or her first birthday. Arthur Morrison wrote the influential A Child of the Jago, an account of the life of a child in the slum, which sparked a public outcry. Construction of the Boundary Estate was begun in 1890 by the Metropolitan Board of Works and completed by the recently formed London County Council in 1900. The success of this project spurred many local councils to embark on similar construction schemes in the early 20th century.
-- Wikipedia. "Public housing."
Gentrification in the media
Take This Hammer (documentary of James Baldwin visiting SF, 1963)
Director’s cut, with 15 minutes of footage restored:
Take This Hammer is a documentary film produced and directed by KQED (TV)'s Richard O. Moore for National Educational Television in 1963.The film first aired on February 4, 1964 in the Bay Area, at 7:30pm on Ch.9 KQED.
It features KQED's mobile film unit following author and activist James Baldwin in the spring of 1963, as he's driven around San Francisco to meet with members of the local African American community. He is escorted by Youth For Service's Executive Director Orville Luster and trying to establish: "The real situation of Negroes in the city, as opposed to the image San Francisco would like to present." He declares: "There is no moral distance ... between the facts of life in San Francisco and the facts of life in Birmingham. Someone's got to tell it like it is. And that's where it's at." Baldwin has frank exchanges with local people on the street and meets with community leaders in the Bayview and Western Addition neighborhoods. He also reflects on the racial inequality that African Americans are forced to confront and at one point tries to lift the morale of a young man, by expressing his conviction that: "There will be a Negro president of this country but it will not be the country that we are sitting in now."
South Park "The City Part of Town," 2015 
The process of gentrification was satirically examined in animated TV show South Park, Season 19 Episode 3, "The City Part of Town." which aired on September 30, 2015.. Episode summary from Wikipedia:
Following Mr. Garrison's anti-immigration campaigning in the previous episode, South Park is ridiculed by Jimmy Fallon on TV. To counter the bad publicity, the town decides to convince Whole Foods Market to build a store there. This requires passing a thorough inspection with a representative of the firm, so Mayor McDaniels, with the help of Randy Marsh, decides to build a fancy and modern gentrified district, SodoSopa ("South of Downtown South Park"). The new district is intentionally built around Kenny[McCormick]'s dilapidated home to appeal to young hipsters who enjoy the "rustic charm" of the scenery. SodoSopa runs several commercials (filmed in live action) advertising that all of the new restaurants and shops are "supporting" the original poor residents — when in fact no one in Kenny's family actually works at any of them. Soon the new district starts building middle-class apartment units for customers and employees to live in — all while claiming that this is revitalizing the poor residents that it was simply built around.
Saturday Night Live, "Bushwick, Brooklyn 2015"
"Hanging out on a street corner in Bushwick, Brooklyn is quite a bit different now than it used to be. There are still bodegas here and there, but they're mixed in with plenty of organic markets and farm-to-table, nose-to-tail brunch spots -- or, as "Saturday Night Live" would have it, the occasional "artisanal mayonnaise" shop.
"In a brilliant sketch about gentrification, three friends -- Keenan Thompson, Jay Pharaoh and this week's host, Kevin Hart -- hang out in their neighborhood and discuss what they've been up to of late. Recent activities include: Eating gelato on the street, painting landscapes while sipping white wine and hanging out with their "bitches" -- which, in Bushwick 2015, means running a booming dog-walking business."
- Jenny Kutner. “‘SNL’ brilliantly tackles gentrification.” Salon, 18 Jan 2015.
Neil Young, "Old Man" (1971)
Written about his purchase of Broken Arrow Ranch on the San Francisco peninsula near La Honda:
"About that time when I wrote ("Heart of Gold"), and I was touring, I had also—just, you know, being a rich hippie for the first time—I had purchased a ranch, and I still live there today. And there was a couple living on it that were the caretakers, an old gentleman named Louis Avila and his wife Clara. And there was this old blue Jeep there, and Louis took me for a ride in this blue Jeep. He gets me up there on the top side of the place, and there's this lake up there that fed all the pastures, and he says, "Well, tell me, how does a young man like yourself have enough money to buy a place like this?" And I said, "Well, just lucky, Louis, just real lucky." And he said, "Well, that's the darnedest thing I ever heard." And I wrote this song for him.
- List of top 15 gentrifying neighborhoods in New York City (2016)
- Urban renewal
- Atkinson, R, & G. Bridge (eds), Gentrification in a global context: the new urban colonialism (256-64). London, New York: Routledge.
including: Clark, E. “The order and simplicity of gentrification: A political challenge.”
- Bhakta, Chirag. “We will not be gentrified: In defense of the Tenderloin.” Op-ed, San Francisco Examiner, 11 November 2016. http://www.sfexaminer.com/will-not-gentrified-defense-tenderloin/.
- Brown, Stephanie."Beyond Gentrification: Strategies for Guiding the Conversation and Redirecting the Outcomes of Community Transition." Harvard Joint Center for Housing Studies, July 2014. http://www.jchs.harvard.edu/research/publications/beyond-gentrification-strategies-guiding-conversation-and-redirecting-outcomes.
- Causa Justa::Just Cause. "Development without Displacement: Resisting Gentrification in the Bay Area." 2014 report. https://cjjc.org/publication/development-without-displacement-resisting-gentrification-in-the-bay-area/.
- Clark, E. (2005). “The order and simplicity of gentrification: A political challenge.” In R. Atkinson & G. Bridge (eds), Gentrification in a global context: the new urban colonialism (256-64). London, New York: Routledge.
- Cortright, Joe. “In Defense of Gentrification.” The Atlantic, OCT 31, 2015.
"The prevailing narrative ignores an abundance of evidence that relatively few low-income neighborhoods get gentrified—and when they do, there’s much less displacement than is commonly assumed."
- Couture, Victor, and Jessie Handbury. "Urban Revival in America, 2000 to 2010.” Free version May 2017 https://bfi.uchicago.edu/sites/default/files/research/3_CoutureHandbury_UrbanRevival_Paper_Chicago.pdf.
"This paper documents and explains the striking reversal of fortune of urban America from 2000 to 2010. We show that almost all large American cities have experienced rising numbers in young professionals near their city center over the last decade. We assemble a rich database at a fine spatial scale to test a number of competing hypotheses explaining this recent trend. We first estimate a residential choice model to assess the relative roles of amenities, job locations, and housing prices in drawing the young and college-educated downtown. We find that initial conditions of non-tradable service amenities explain the diverging location decisions of the young and college-educated relative to their non-college-educated peers and their older college-educated counterparts. The coefficients on these initial conditions suggest that preferences for these amenities are changing over time. We investigate this hypothesis using complementary datasets, where we find that non-tradable service amenities are also playing an increasingly dominant role in the expenditure and travel decisions of the young and college educated relative to other groups. Finally, we show that these new trends are partially explained by the changing income composition and family structure of the young and college-educated and strongly related to opportunities to network and socialize with other young professionals."
- Curl, S. (2006) A dictionary of architecture and landscape architecture. Oxford (England, UK: Oxford University Press.)
- FireWorks (@FireWorksBAY). "March Against #Gentrification in West #Oakland Tonight." Twitter post, with image of anti-gentrification poster, 11 June 2014. https://twitter.com/FireWorksBAY/status/476797876761157632.
[provided to journalist Sam Levin (see citation) by acquaintance of YIMBYwiki whose West Oakland business was vandalized on the night of that post, apparently by anti-gentrification protestors. -ed].
- Gammon, Robert. "The Real Cause of Gentrification" Oakland Magazine May 2017.
cover story with photo featuring and story quoting YIMBY organizer Victoria Fisher, founder of East Bay Forward. http://www.oaklandmagazine.com/May-2017/The-Real-Cause-of-Gentrification/.
- Glass, Ruth (1964). London: aspects of change. London: MacGibbon & Kee.
- Godsil, Rachel D. “Transforming Gentrification into Integration.” NYU Furman Center, May 2014.
- Goetze, Understanding Neighborhood Change, 1979.
Apparent first use of "filtering up" as a term or definition for gentrification.
- Greenberg, Michael. “Tenants Under Siege: Inside New York City’s Housing Crisis.” The New York Review of Books, 17 August 2017. http://www.nybooks.com/articles/2017/08/17/tenants-under-siege-inside-new-york-city-housing-crisis/.
- Grier and Grier . “Urban Displacement: A Reconnaissance." U.S. Department of Housing and Urban Development (HUD).
- Guerrieri, Veronica; Daniel Hartley, Erik Hurst (2010). “Endogenous Gentrification and Housing Price Dynamics.” NBER Working Paper 16237, July 2010. http://www.nber.org/papers/w16237.
In this paper, we begin by documenting substantial variation in house price growth across neighborhoods within a city during city wide housing price booms. We then present a model which links house price movements across neighborhoods within a city and the gentrification of those neighborhoods in response to a city wide housing demand shock. A key ingredient in our model is a positive neighborhood externality: individuals like to live next to richer neighbors. This generates an equilibrium where households segregate based upon their income. In response to a city wide demand shock, higher income residents will choose to expand their housing by migrating into the poorer neighborhoods that directly abut the initial richer neighborhoods. The in-migration of the richer residents into these border neighborhoods will bid up
prices in those neighborhoods causing the original poorer residents to migrate out. We refer to this process as "endogenous gentrification". Using a variety of data sets and using Bartik variation across cities to identify city level housing demand shocks, we find strong empirical support for the model's predictions.”
- Immergluck, Dan. "Sustainable for Whom? Large-Scale Sustainable Urban Development Projects and “Environmental Gentrification.” Shelterforce, 1 September 2017.
- Kutner, Jenny. “‘SNL’ brilliantly tackles gentrification.” Salon, 18 Jan 2015.
- Lees, Loretta, Tom Slater, and Elvin Wyly, editors. The Gentrification Reader. 2010. Amazon.
Table of contents and introduction.
- Levin, Sam. "West Oakland's Kilovolt Coffee Vandalized After Controversial Redevelopment Plan Gains Approval." East Bay Express, June 12, 2014.
- Lewyn, Michael. "Does the Threat of Gentrification Justify Restrictive Zoning?". Real Estate Law Journal (2017) @mlewyn https://works.bepress.com/lewyn/150/. @mlewyn
[he argues, generally no].
"Abstract: Historically, progressives have opposed restrictive zoning, arguing that by restricting the housing supply to high-end housing, zoning reduces the supply of housing available to lower-income Americans. But recently, some progressives have suggested that new market-rate housing facilitates gentrification and displacement of lower-income renters. This article critically examines that theory."
- Marcuse, Peter. "Gentrification, Abandonment, and Displacement: Connections, Causes, and Policy Responses in New York City." Urban Law Annual ; Journal of Urban and Contemporary Law, Volume 28 (January 1985). http://openscholarship.wustl.edu/cgi/viewcontent.cgi?article=1396&context=law_urbanlaw.
- Matthews, Mark, and Lisa Fernandez. "Kilovolt Coffee Shop Owner Suspects West Oakland Gentrification "Haters" of Attacking His Business." NBC Bay Area, June 14, 2014. http://www.nbcbayarea.com/news/local/Kilovolt-Coffee-in-Oakland-Vandalized-Gentrification-263069321.html.
- Patch, Jason, and Neil Brenner (2007). "Gentrification." in The Blackwell Encyclopedia of Sociology. 15 FEB 2007. DOI: 10.1002/9781405165518.wbeosg035. http://onlinelibrary.wiley.com/doi/10.1002/9781405165518.wbeosg035/abstract.
- Perez, Gina. The Near Northwest Side Story: Migration, Displacement, and Puerto Rican Families. 2004.
- Proud, Alex. "Why this 'Shoreditchification' of London must stop." The Telegraph, 13 January 2014. http://www.telegraph.co.uk/men/thinking-man/why-this-shoreditchification-of-london-must-stop/.
- Ross, Benjamin. Dead End: Suburban Sprawl and the Rebirth of American Urbanism. (Oxford University Press, 2014). Amazon.
- Schlichtman, John Joe. "How the Unwilling Gentrifier Buys a Home: A diary of my attempt to make an ethical housing choice in Chicago." Next City, May 8, 2017 https://nextcity.org/features/view/unwilling-gentrifier-buys-home-book-excerpt. (an excerpt from Schlichtman, John Joe, Jason Patch and Marc Lamont Hill. Gentrifier. (2017).
- Schlichtman, John Joe; Jason Patch, and Marc Lamont Hill. Gentrifier. 2017.
- Slater, Tom. “Missing Marcuse: On gentrification and displacement.” City. 1 June 2009.
- Smith, Neil (1996). The New Urban Frontier: Gentrification and the revanchist city.” London, New York: Routledge.
- Smith, Neil (2000). “Gentrification.” in R. J. Johnston, Derek Gregory, Geraldine Pratt, Michael Watts (eds). Dictionary of Human Geography, 4th edition. 2000.
- Smith, Neil, and Peter Williams (Eds). Gentrification of the City. 1986.
- South Park. "The City Part of Town" (Season 19, Episode 3).
- Wynn, Jonathan, and Andrew Deener. “Gentrification? Bring it.” The Conversation. October 10, 2017,
- Zuk, Miriam, and Ariel H. Bierbaum, Karen Chapple, Karolina Gorska, Anastasia Loukaitou-Sideris, Paul Ong, and Trevor Thomas. "Gentrification, Displacement and the Role of Public Investment: A Literature Review". Federal Reserve Bank of San Francisco (Working Paper), August 24, 2015. http://www.frbsf.org/community-development/publications/working-papers/2015/august/gentrification-displacement-role-of-public-investment/.
[funded by the California Air Resources Board as part of the project “Developing a New Methodology for Analyzing Potential Displacement.”]
- Zuk, Miriam, and Karen Chapple. "Housing Production, Filtering and Displacement: Untangling the Relationships." UC Berkeley Institute of Governmental Studies, Research Brief, May 2016. .