You cannot serve two masters. 【谚】 一身难侍二主
He served the country as a diplomat for thirty years. 他作为外交官为国家服务了三十年.

serve a customer in a store 在商店接待顾客
Are you being served? (侍者招呼客人用语)您要东西了吗?

serve one's apprenticeship 当学徒
serve one's time 做满任期;(囚犯)服刑
serve a sentence (囚犯)服刑
serve two terms as President 担任两届总统
serve one's mayoralty 任市长之职.

serve sb's turn [need] 对某人合用
This will serve my purpose. 这会合我用的
Let me know if I can serve you in any way. 如有我可以帮忙之处,但说无妨.
Ten pounds serve him for a week. 十镑够他花一个星期
if memory serves (me) 如果我没有记错的话
This railway serves a great district. 这条铁路可满足广大地区的需要.

The dairy serves us with milk. 牛奶公司向我们供应牛奶.

The maid served the first course. 女仆端上了第一道菜.
Dinner is served. 请就座,请用膳(意为:饭菜摆好了). (Dinner is ready.)
She served beer to them [served them with beer]. 她给他们端上啤酒.
She served us a very good dinner. 她侍候我们吃了一顿很丰盛的饭.

serve a ball 发球
serve a fault 发球失误.

serve a summons on sb=serve sb (with) a summons 向某人送达传票.

She served me ill. 她待我不好.
It serves [【口】 Serve(s)] you [him, etc.] right! 你[他]活该!

serve as a clerk in a bank 在银行当职员.
serve with [in] the army [company] 在陆军中服役[在公司当职员]
serve on the committee 担任委员会委员
His grandfather served under Lincoln. 他祖父在林肯手下供职.
serve behind a counter 当店员,站柜台.

This tool serves for many purposes. 这个工具有许多用途.
Many of the stars have served as guides for mariners. 有不少星星都能给水手指示方向.
This paper will serve to build a fire. 这张纸就足以点火.
When the tide serves,... 在潮水合适时,…
as memory [occasion] serves 衹要想起来[一有适当机会].

He served well [badly, poorly]. 他发球发得好[不好].