noun, noun which may take the genitive case particle 'no'
filling a vacancy; supplementation
Refers to the act or system of filling an empty position, often in an organization or team. Can be used as a noun or with の to modify another noun.
欠員が出たので、補欠の手続きを急いだ。
Since a vacancy opened up, we hurried the process of filling it.
補
A by-election will be held next month.
noun
A person who stands by to take over a role when needed, such as a substitute player in sports or an alternate member of a committee.
彼はサッカー部の補欠だ。
He is a substitute on the soccer team.
補欠の選手が急に出場することになった。
The substitute player suddenly had to take the field.