Ain’t is a centuries-old contraction meaning am not, is not, are not, has not, or have not. The word has been derided by usage authorities throughout its history, and it’s still considered unacceptable in formal writing, but it has a secure place in spoken English. In edited writing, ain’t is mainly used tongue-in-cheek, as part of a common expression, or in an effort to sound folksy.
Let’s face it, surfers and surfettes, when the water temps in the high 30s or low 40s, it ain’t much fun. [Star-Ledger]
A lot of people say if it ain’t broke, don’t fix it. [Mirror]
Northeast England ain’t renowned for its winemakers, but Andrew Hedley of Framingham isn’t your average guy. [New Zealand Herald]
This ain’t your grandmother’s Lladró. [Los Angeles Times]