The term “tenement” simply refers to a building that is divided into apartments for the use of multiple residents, but it has come to have a pejorative meaning, thanks to the history of such buildings around the world. Therefore, it is unusual to hear an ordinary apartment building referred to by this term, except in some isolated regions of the world where its negative meaning has not penetrated.
The defining characteristic of a tenement is that it is a building divided into three or more apartments, and these apartments are leased from a landlord who owns the entire building. Many buildings have vast numbers of apartments and multiple stories to accommodate them all.
In the United States, tenements housed the majority of new immigrants to the country in the 19th and early 20th century. These buildings were cramped, crowded, and poorly constructed. Often, multiple families lived in the same apartment together to save rent, leaving minimal space, and the buildings were poorly ventilated. Many also lacked water and basic sanitation, and they were probably extremely unpleasant to live in.
Tenements may have been unpleasant, but their landlords were often worse. Landlords would take advantage of new immigrants with price gouging tactics, intimidation, and other techniques designed to keep the tenants from complaining or reporting hazardous conditions. Fires were common, along with the spread of infectious disease. As a result of these conditions, the term often conjures up the image of cheaply made working class housing for many Americans, and this sense of the word has spread to many other regions of the world.
Particularly infamous were the tenements in New York City, and many organizations crusaded to create protections for residents and legislate at least basic measures for human decency, like minimum space requirements, mandatory air shafts for ventilation, and basic plumbing for the purpose of sanitation. Today, all construction in the United States is closely regulated, and people would be hard pressed to find conditions as extreme as those that prevailed in the late 1800s, although housing of very poor quality still exists.
Many people associate tenements with slums, again thanks to the early examples in the United States. In some regions of the word, high-quality apartment housing has devolved, creating slums where pleasant neighborhoods once existed. The rise of slums is caused by a number of factors, including changing fortunes, shifting property values, and increasing migration into cities from rural areas.