If not
If not adverb - Perhaps; indicating possibility of being more remarkable (greater or better or sooner) than.
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Synonyms for If not
What if and if not are semantically related. In some cases you can use "What if" instead a conjunction phrase "If not".
What if
If not and what if are semantically related. Sometimes you can use "If not" instead a conjunction phrase "What if".
Mutual synonyms
Both terms in one sentence
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Beethoven Was an Alien Spy: If not actually the first story to be built on the idea of 'hey, what if H. G.
Source: Film / Time After Time - This would be bad enough if you could class all other uses of the lighter as "silly" and disallow them - but what if there are places where starting a fire is, if not optimal, a not-entirely-unreasonable solution?
Source: Combinatorial Explosion
Cite this Source
What if and If not. (2016). Retrieved 2026, August 03, from https://thesaurus.plus/related/if_not/what_if
If not & What if. N.p., 2016. Web. 03 Aug. 2026. <https://thesaurus.plus/related/if_not/what_if>.
What if or If not. 2016. Accessed August 03, 2026. https://thesaurus.plus/related/if_not/what_if.
Google Ngram Viewer shows how "if not" and "what if" have occurred on timeline