じゃない ⇒ ちゃうTo be not, Am not, Are not, Is not

The negative form of the auxiliary verb だ in Japanese frequently appears as じゃない (an abbreviation of ではない). In 関西弁(かんさいべん) じゃない is often replaced by ちゃう. ちゃう itself is actually just an abbreviation of 違(ちが)う, a common うverb meaning 'to differ'.

ちゃう may be used directly after either nouns, or な-Adjectives, to convey 'is not (A)'.

ちゃう may also appear in the past negative form. However, as it is a set expression (and not considered an actual conjugation of 違(ちが)う), it will not be conjugated like a regular う - Verb, but will become ちゃうかった.

Fun Fact

じゃない may also be replaced with やない. やない being the 関西弁(かんさいべん) equivalent of だ, with the い-Adjective ない attached to it. Like ちゃう, やない is used after nouns, or な-Adjectives.

When conjugating in the past negative form, やない follows the regular conjugation rules of ない, becoming やなかった.