机

In a sentence

• 私は新しい机を買いました。

  I bought a new desk.

  Here, '机' specifically refers to a desk, which is a piece of furniture used for writing or working.

• 机の上に本があります。

  There is a book on the desk.

  In this sentence, '机' refers to the desk as a physical location where objects can be placed on.

• この机はとても重いです。

  This desk is very heavy.

  Here, '机' is used to describe the desk in terms of its properties, specifically its weight.