There are two main categories of adjective: i-adjectives and na-adjectives. I'll describe how to identify and use na-adjectives later.
I-adjectives
- end in i in present affirmative form
- the final i must be preceded by a, i, u, or o, but never by e
- in present affirmative form, they are followed by desu
- to create present negative form, replace the final i with ku, then add arimasen afterwards
- to create past affirmative form, replace the final i with katta and add desu
- to create past negative form, add deshita after the present negative
Examples of i-adjectives
Present affirmative - warui, takai, yasui, chiisai, akarui
Present negative - waruku arimasen, takaku arimasen, yasuku arimasen, chiisaku arimasen, akaruku arimasen
Past affirmative - warukatta desu, takakatta desu, yasukatta desu, chiisakatta desu, akarukatta desu
Past negative - waruku arimasen deshita, takaku arimasen deshita, yasuku arimasen deshita, chiisaku arimasen deshita, akaruku arimasen deshita
Some sentences:
Asagohan wa takai desu. (Breakfast is expensive.)
Hirugohan wa takaku arimasen. (Lunch is not expensive.)
Bangohan wa takakatta desu. (Dinner was expensive.)
Bangohan wa takaku arimasen deshita. (Dinner was not expensive.)