sly vs su, What's the Difference?

Which to use

“sly” is an adjective and “su” is a noun - they look or sound alike but fill different roles in a sentence.

#17,246
“sly” frequency rank: #8,094
“su” frequency rank: 25340
confusion score

Side-by-Side Comparison

Feature	sly	su
Definition	Artfully cunning; secretly mischievous; wily.	Alternative form of xu (“former Vietnamese currency”).

Letter map: sly vs su

Shared letters muted; letters that set sly and su apart highlighted. Shared run: 1.

3 ch

sly

2 ch

Role in the sentence - sly and su

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: sly is anadjective and suanoun. On the page they differ by 1 letter(s) in length. Our composite confusion score for this pair is 25340, derived from the frequency rank of both members and their visual similarity.

sly is recorded at frequency rank #17,246, classified as anadj, pronounced /slaɪ/. su is at rank #8,094, tagged as anoun.

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 25340, this pair ranks #395,032 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of sly vs su

Shared letters: s. Private to "sly": ly. Private to "su": u.

"sly" · 3 letters · shape CCV · "su" · 2 letters · shape CV

Frequently Asked Questions

Is swapping "sly" for "su" ever safe?

No - they are not even the same part of speech. "sly" is an adjective and "su" a noun, so a sentence built for one is usually ungrammatical with the other.

Frequency check: "sly" vs "su" - which ranks higher?

"su" is the more common of the two: it sits at frequency rank #8,094 in our English list, against #17,246 for "sly". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

After this comparison

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

Full dictionary entry for "sly" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "su" - compare definitions side by side with the headword page. Word entry
This pair ranks #395,032 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
"sly" and "su" also get mixed up with nearby pairs, the highest-scored neighbour is "Sif vs sly". Nearby pair

Confusion rank #395,032 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.