Square
Rectangle, Cube
noun, な adjective, の adjective
What shape has four angles? The most common one is a square, but it could also be a rectangle or even a cube.
This is a jukugo word that uses the on'yomi readings for the kanji. You've learned them both already, so you should be able to read this word!
わたしのキーボードのキーは四角です。
The keys on my keyboard are square.
日本の切手は主に四角ですよ。
Japanese stamps are mainly rectangular.
「口」と言う字は、ただの四角に見えませんか？
Doesn't the character for "kuchi" look like a square?