— used to say that the people who arrive earliest get served or treated before the people who arrive later先来先接待;先来先供应;按先来后到的原则
The campsites are first come, first served, so we'd better get there early. = The campsites are assigned on a first-come-first-serve basis, so we'd better get there early.露营帐篷搭建地是先到先得,所以我们最好早点到那儿。
“Aren't there any cookies left?” “Sorry—first come, first served.”“还有饼干吗?”“对不起,已经没了,先来先得。”