why vs why's, What's the Difference?

Which to use

“why” is an adverb and “why's” is a contraction - they look or sound alike but fill different roles in a sentence.

#125
“why” frequency rank: #28,792
“why's” frequency rank: 28917
confusion score

Side-by-Side Comparison

Feature	why	why's
Definition	For what cause, reason, or purpose.	Contraction of why + is.

Letter map: why vs why's

Shared letters muted; letters that set why and why's apart highlighted. Shared run: 3. why runs 3 letters (CCV) against why's's 4 (CCVC) - the length gap alone is often enough to separate them once you know to check it.

3 ch

why

5 ch

why's

Part-of-speech tell for why / why's

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: why is anadverb and why'sacontraction. On the page they differ by 2 extra letter(s) - “why” sits inside “why's”. Our composite confusion score for this pair is 28917, derived from the frequency rank of both members and their visual similarity.

why is recorded at frequency rank #125, classified as anadv, pronounced /wæ/. why's is at rank #28,792, tagged as acontraction.

Glosses for this pair are partially populated in our dataset, but the full side-by-side definitions above should still guide you to the right choice.

With a confusion score of 28917, this pair ranks #367,236 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of why vs why's

Shared letters: hwy. Private to "why": -. Private to "why's": s.

"why" · 3 letters · shape CCV · "why's" · 4 letters · shape CCVC

Frequently Asked Questions

Can "why" and "why's" be used interchangeably?

No - they are not even the same part of speech. "why" is an adverb and "why's" a contraction, so a sentence built for one is usually ungrammatical with the other.

In ordinary English text, does "why" or "why's" show up more?

"why" is the more common of the two: it sits at frequency rank #125 in our English list, against #28,792 for "why's". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

What to do next

You've compared "why" and "why's". Here's where to go from here.

Full dictionary entry for "why" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "why's" - compare definitions side by side with the headword page. Word entry
This pair ranks #367,236 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
"why" and "why's" also get mixed up with nearby pairs, the highest-scored neighbour is "why's vs Whyte". Nearby pair

Confusion rank #367,236 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.