• 四よん — four
• 四よっつ — four (general counter)
• 四人よにん — four people
• 四月しがつ — April
• 四季しき — four seasons
• 四角形しかくけい — square / quadrilateral
• 第四だいよん — the fourth
• 四捨五入ししゃごにゅう — rounding (fractions)

四 is a basic counting kanji, but it has two common readings. In daily conversation, よん is preferred, while し appears in set words like 四月. Understanding when each reading is used helps learners sound more natural.