In the Japanese language, not only verbs, but also adjectives, conjugate. The adjective 'warm' is 'atatakai' in Japanese. As an example, the following is a verb conjugation in English: It is warm; It is not warm; It was warm; It was not warm. The same conjugation in Japanese is as follows: Atatakai desu; Atatakakunai desu; Atatakakatta desu; Atatakakunakatta desu. It is like a tongue-twister because it is incredibly difficult to manipulate the tongue to say 'atatakakunakatta desu' (It was not warm). Many students of mine try to say this fast and fail. Then we burst into laughter.