client

client
/ˈklaɪənt; `klaɪənt/ n
1 person who receives help or advice from a professional person (eg a lawyer, an accountant, a social worker, an architect, etc) （律师、 会计师、 社会工作者、 建筑师等的）委托人, 当事人.
2 customer in a shop （商店的）顾客, 主顾.

牛津英汉双解词典