「四」(yon) means "four" or "4". It's commonly used for counting things or people. Be aware it can also be read as "shi," but "yon" is often preferred when counting by itself or in certain contexts to avoid sounding like "death" (死). Example: 「四つ」(yottsu) means "four things".

「四(よん)」は「4」を意味(いみ)します。「し」と読(よ)むこともあります。数(かず)を数(かぞ)える時(とき)に使(つか)います。例(れい)：「四(よっ)つ」。