Meaning of CERTAIN in English
adj. & pron.
adj. 1 a (often foll. by of, or that + clause) confident, convinced (certain that I put it here). b (often foll. by that + clause) indisputable; known for sure (it is certain that he is guilty). 2 (often foll. by to + infin.) a that may be relied on to happen (it is certain to rain). b destined (certain to become a star). 3 definite, unfailing, reliable (a certain indication of the coming storm; his touch is certain). 4 (of a person, place, etc.) that might be specified, but is not (a certain lady; of a certain age). 5 some though not much (a certain reluctance). 6 (of a person, place, etc.) existing, though probably unknown to the reader or hearer (a certain John Smith).
pron. (as pl.) some but not all (certain of them were wounded). for certain without doubt. make certain = make sure (see SURE).
[ ME f. OF ult. f. L certus settled ]
Concise Oxford English dictionary. Краткий оксфордский словарь английского языка. 2012