In grammar, a change in form (conjugation) where verbs, adjectives, etc., do not follow regular patterns and alter individually; treated as exceptions in learning.
日本語の「来る」は不規則変化の例で、来ます／来ないなどと活用する。
The Japanese verb 'kuru' is an example of an irregular conjugation; it conjugates as kuru/ kimasu / konai, etc.
英語でも不規則変化の動詞（go→wentなど）は早めに覚えるとよい。
In English, it's good to learn irregular verbs (go→went, etc.) early on.
教科書の巻末には不規則変化の一覧が載っていることが多い。
Textbooks often include a list of irregular conjugations at the back.