hanamaru
Describe how something is
An い-adjective describes a noun and can sit at the end of a sentence on its own.
JLPTN5
い-adjective + (です)~i (+ desu)
describe something with an い-adjective
Example Sentences
That mountain is tall, isn't it
This shop is cheap!
These adjectives end in い and can finish a sentence on their own — no copula needed, though you add です to be polite. That final い is the part that changes: swap it for くない to negate (たかい→たかくない) and for かった for the past (たかい→たかかった).
Conjugation
高い→高く
adverbial
高い→高かった
past
高い→高くない
negative
Tips and Common Traps
Hana· Key point
Use い-adjectives to paint a picture — drop one in front of any noun and your sentence comes alive: 大きい犬 (big dog), 青い空 (blue sky).
Maru· Common trap
いい (good) is irregular — its negative is よくない, not いくない. Every other い-adjective follows the pattern.