“一日为侦探，终生为侦探，”他满不在意地说。用英语怎么说？

“一日为侦探，终生为侦探，”他满不在意地说。

"Once a detective, always a detective," he said lightly.

once

adv. 一次，一趟，一倍，曾经，一旦；conj. 一旦…就…，一经；n. 一次，一回；

例句
The Hell's Angels were once the most notorious and anarchistic of motorbike gangs.
“地狱天使”曾是飞车党中最臭名昭著和无法无天的一伙。

detective

adj. 侦探的，适于探测的，用于探测的；n. 侦探；

例句
The detective has to discover the motive, the means and the opportunity and has to keep these three balls in the air.
那名侦探必须查明动机、手段和时机，而且对这三项的调查必须同步展开。

always

adv. 总是，老是，永远，始终，常常，不断地；

例句
Some cities are always going to be more advantaged.
一些城市总会有一些得天独厚的优势。

he

pron. 他，它，一个人；n. 雄性动物；

例句
Logic had prevailed and he had abandoned the idea.
最终理智占了上风，他打消了那个念头。

said

adj. [律]上述的，少说为妙，（做）某事有/没有很多优点（或好处）：某事物有/没有多少可说的，说到底；v. 说，讲( say的过去式和过去分词 )，表明，念，说明；

例句
They said goodbye to him as he got aboard the train at Union Station.
当他在联合火车站登上火车之际，他们向他道别。

lightly

adv. 轻轻地，轻巧地，轻松地，轻快地，轻易地，容易地，不费力地，轻率地；

例句
Despite his bulk he moved lightly on his feet.
尽管他身形庞大，移动起来还是很灵巧。