[sur-tn] 
| 1. | free from doubt or reservation; confident; sure: I am certain he will come. |
| 2. | destined; sure to happen (usually fol. by an infinitive): He is certain to be there. |
| 3. | inevitable; bound to come: They realized then that war was certain. |
| 4. | established as true or sure; unquestionable; indisputable: It is certain that he tried. |
| 5. | fixed; agreed upon; settled: on a certain day; for a certain amount. |
| 6. | definite or particular, but not named or specified: A certain person phoned. He had a certain charm. |
| 7. | that may be depended on; trustworthy; unfailing; reliable: His aim was certain. |
| 8. | some though not much: a certain reluctance. |
| 9. | Obsolete. steadfast. |
| 10. | certain ones: Certain of the members declined the invitation. |
| 11. | for certain, without a doubt; surely: I know for certain that I have seen that face before. |
| cer·tain (sûr'tn) adj.
[Middle English, from Old French, from Vulgar Latin *certānus, from Latin certus, past participle of cernere, to determine; see krei- in Indo-European roots.] Synonyms: These adjectives mean impossible to avoid or evade: soldiers who knew they faced certain death; facts that led to an inescapable conclusion; an inevitable result; sudden but sure retribution; an unavoidable accident. See Also Synonyms at sure. Usage Note: Although certain appears to be an absolute term, it is frequently qualified by adverbs, as in fairly certain or quite certain. In an earlier survey a majority of the Usage Panel accepted the construction Nothing could be more certain. |
for certain
Also, for sure. Without doubt. For example, I can't tell for certain if this is the right color, or I know for sure that she has a new car. The first term dates from the early 1300s. The variant, dating from the late 1500s, is also used colloquially to express agreement or assert the truth of a statement, as in Mary is really bossy.
That's for sure, or Are you coming to the party?For sure I am.
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