In Japanese, い-adjectives can directly modify a noun by placing them immediately before it – no particle or conjugation is needed. The adjective keeps its final い and simply attaches to the noun.
This is one of the simplest and most fundamental patterns in Japanese. Unlike な-adjectives, which require な before the noun, い-adjectives connect directly.
The modified noun phrase can be used anywhere a regular noun would appear – as a subject, object, or part of a larger sentence.
You can stack multiple adjectives before a noun, though it is more natural to connect them using the 〜~くて (te-form) of the い-adjective.
The adjective いい (good) is irregular. When modifying a noun it stays as いい:
However, when conjugated (past, negative, te-form, etc.), it changes to the よい stem (e.g. よかった, よくない).