1. Definite; fixed: set aside a certain sum each week.
2. Sure to come or happen; inevitable: certain success.
3. Established beyond doubt or question; indisputable: What is certain is that every effect must have a cause.
4. Capable of being relied on; dependable: a quick and certain remedy.
5. Having or showing confidence; assured: I'm certain I left my keys in this room.
a. Not specified or identified but assumed to be known: felt that certain breeds did not make good pets.
b. Named but not known or previously mentioned: a certain Ms. Johnson.
7. Perceptible; noticeable: a certain charm; a certain air of mystery.
8. Not great; calculable: to a certain degree; a certain delay in the schedule.
An indefinite but limited number; some: Certain of the products are faulty.
Without doubt; definitely.
[Middle English, from Old French, from Vulgar Latin *certānus, from Latin certus, past participle of cernere, to determine; see krei- in the Appendix of Indo-European roots.]
Synonyms: certain, inescapable, inevitable, sure, unavoidable
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: It is often claimed that certain is an absolute term like unanimous or paramount and cannot be modified; something is either certain or it is not. However, a majority of the Usage Panel accepted the construction Nothing could be more certain as early as 1965, and phrases such as fairly certain and quite certain are readily understood as expressing varying degrees of confidence, especially when they refer to a person. Phrases in which certain is modified can be quite effective, as the following example from Susan Orlean shows: "The [taxidermic] piece was precise and lovely, almost haunting, since the more you looked at it the more certain you were that the birds would just stop building their nest, spread their wings, and fly away." Note that since certain must always suggest overall confidence, its range is restricted to the upper range; one is less likely to be slightly, somewhat, or a little bit certain, for example.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.