su vs sub, What's the Difference?

Which to use

“su” is a verb and “sub” is a preposition - they look or sound alike but fill different roles in a sentence.

#1,609
“su” frequency rank: #10,413
“sub” frequency rank: 12022
confusion score

Side-by-Side Comparison

Feature	su	sub
Definition	Participe passé masculin singulier du verbe savoir.	Préposition latine, qui s’emploie dans des locutions telles que :

Where the eye mixes su and sub

Muted = shared; highlighted = the visual trap. They share 2 letters in sequence.

2 ch

3 ch

sub

Why the eye confuses su with sub

These two trip readers on the page rather than in the ear: su is \sy\ while sub is \syb\. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 extra letter(s) - “su” sits inside “sub”, and the parts of speech differ too (verb vs preposition), which is usually the fastest check. Our composite confusion score for this pair is 12022, derived from the frequency rank of both members and their visual similarity.

su is recorded at frequency rank #1,609, classified as averb, pronounced \sy\. sub is at rank #10,413, tagged as aprep, pronounced \syb\.

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 12022, this pair ranks #406,879 of 440,172 scored French confusable pairs - a relatively easy-to-tell-apart pair.

Orthographic DNA of su vs sub

Shared letters: su. Private to "su": -. Private to "sub": b.

"su" · 2 letters · shape CV · "sub" · 3 letters · shape CVC

Frequently Asked Questions

Do "su" and "sub" mean the same thing in a sentence?

No - they are not even the same part of speech. "su" is a verb and "sub" a preposition, so a sentence built for one is usually ungrammatical with the other.

In ordinary French text, does "su" or "sub" show up more?

"su" is the more common of the two: it sits at frequency rank #1,609 in our French list, against #10,413 for "sub". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

What to do next

Visual near-miss handled. Browse the word pages or a neighbour when the next look-alike shows up.

Full dictionary entry for "su" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "sub" - compare definitions side by side with the headword page. Word entry
This pair ranks #406,879 of 440,172 scored French confusable pairs in this corpus vintage. Corpus statistics
"su" and "sub" also get mixed up with nearby pairs, the highest-scored neighbour is "sub vs suu". Nearby pair

Confusion rank #406,879 of 440,172 scored French pairs, corpus vintage 2026-09-03, not spelling advice.