• 副業ふくぎょう — side job
• 副社長ふくしゃちょう — vice president (of a company)
• 副作用ふくさよう — side effect
• 副本ふくほん — duplicate copy
• 副将ふくしょう — vice-captain

副 is made up of the elements 田 (field), 力 (strength), and 刂 (sword/knife). The original meaning relates to something added or attached — like an assistant — or something in duplicate, which explains its use in terms like “副業” (side job) or “副作用” (side effect).

彼かれは 副社長ふくしゃちょうに 就任しゅうにんした。
He was appointed vice president.

>この薬くすりには 副作用ふくさようがあります。
This medicine has side effects.

🎧 “フク” is the on-yomi for this character. It does not have a commonly used kun-yomi. You’ll frequently see it used at the beginning of compound words related to auxiliary or subordinate roles.