sœur vs sur, What's the Difference?

Which to use

“sœur” is a noun and “sur” is a preposition - they look or sound alike but fill different roles in a sentence.

#1,380
“sœur” frequency rank: #26
“sur” frequency rank: 1406
confusion score

Side-by-Side Comparison

Feature	sœur	sur
Definition	Femme ou fille, ayant le même père et la même mère que la personne considérée. Si un seul des parents est commun, c’est une demi-sœur.	Indique une position plus élevée.

Where the spellings diverge

Shared letters are muted; the letters that actually set sœur and sur apart are highlighted. They share 3 letters in sequence, which is exactly why the eye skips the difference.

4 ch

sœur

3 ch

sur

Spelling & Dictionary Insight

These two trip readers on the page rather than in the ear: sœur is \sœʁ\ while sur is \syʁ\. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 letter(s) in length, and the parts of speech differ too (noun vs preposition), which is usually the fastest check. Our composite confusion score for this pair is 1406, derived from the frequency rank of both members and their visual similarity.

sœur is recorded at frequency rank #1,380, classified as anoun, pronounced \sœʁ\. sur is at rank #26, tagged as aprep, pronounced \syʁ\.

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 1406, this pair ranks #438,121 of 440,172 scored French confusable pairs - a relatively easy-to-tell-apart pair.

Orthographic DNA of sœur vs sur

Shared letters: rsu. Private to "sœur": œ. Private to "sur": -.

"sœur" · 4 letters · shape CVVC · "sur" · 3 letters · shape CVC

Frequency comparison

sœur#1,380

sur#26

Source: FrequencyWords open word-frequency list

Frequently Asked Questions

Can "sœur" and "sur" be used interchangeably?

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

Which is more common, "sœur" or "sur"?

"sur" is the more common of the two: it sits at frequency rank #26 in our French list, against #1,380 for "sœur". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

Remembering sœur vs sur

The fastest way to pick the right one every time.

Check the role first: if you need a noun, it's “sœur”; for a preposition, it's “sur”.
See each word in full, definition, IPA, etymology and its other confusables. Full “sœur” entry
Browse more pairs most likely to be confused. Most confusable