1
- able to be firmly relied on to happen or be the case有把握的, 可靠的, 无疑的, 肯定的：
it's certain that more changes are in the offing
毫无疑问, 将会有更多的变化
she looks certain to win an Oscar.
她看来肯定会赢得奥斯卡奖。
1.1
- having or showing complete conviction about something确信的, 毫无疑问的：
are you absolutely certain about this?
这事你能绝对肯定吗？
to my certain knowledge, I've never set eyes on her before.
我确信我从未见过她。
2
- attrib. specific but not explicitly named or stated某种的：
he raised certain personal problems with me
他问了我一些个人问题
the exercise was causing him a certain amount of pain.
这种锻炼使他感到有些疼。
2.1
- used when mentioning the name of someone not known to the reader or hearer某个的（用以提起一个读者或交谈对方不熟悉的姓名）：
a certain General Percy captured the town.
一位叫珀西的将军占领了这座城镇。
pronoun
certain of
- some but not all某些, 某几个：
certain of his works have been edited.
他的某些作品已被校订过了。
短语
for certain
- without any doubt肯定地, 确切地, 无疑地：
I don't know for certain.
我并不确切知道。
make certain
1
- with clause take action to ensure that something happens or is the case（采取行动）确保（某事发生）; 查实（某事）, 查明（某事属实）。
1.1
- establish whether something is definitely correct or true确定（某事是否正确或真实）：
he probably knew her, but it didn't do any harm to make certain.
他很可能认识她, 但确定一下是否如此并没什么坏处。
词源
Middle English: from Old French， based on Latin certus 'settled， sure'.