mm vs MP4, What's the Difference?

Which to use

“mm” is a symbol and “MP4” is a name - they look or sound alike but fill different roles in a sentence.

#1,092
“mm” frequency rank: #49,242
“MP4” frequency rank: 50334
confusion score

Side-by-Side Comparison

Feature	mm	MP4
Definition	Symbole du millimètre, unité de mesure de longueur du Système international (SI), valant 0,001 mètre (10⁻³ mètre).	Norme d’encodage multimédia (audio ou vidéo) sous forme numérique.

Where the spellings diverge

Shared letters are muted; the letters that actually set mm and MP4 apart are highlighted. They share 1 letter in sequence, which is exactly why the eye skips the difference.

2 ch

3 ch

MP4

Spelling & Dictionary Insight

These two trip readers on the page rather than in the ear: mm is \mi.li.mɛtʁ\ while MP4 is \ɛm.pe.katʁ\. 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 (symbol vs name), which is usually the fastest check. Our composite confusion score for this pair is 50334, derived from the frequency rank of both members and their visual similarity.

mm is recorded at frequency rank #1,092, classified as asymbol, pronounced \mi.li.mɛtʁ\. MP4 is at rank #49,242, tagged as aname, pronounced \ɛm.pe.katʁ\.

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 50334, this pair ranks #163,453 of 440,172 scored French confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of mm vs MP4

Shared letters: m. Private to "mm": -. Private to "MP4": p.

"mm" · 2 letters · shape CC · "MP4" · 2 letters · shape CC

Frequency comparison

mm#1,092

MP4#49,242

Source: FrequencyWords open word-frequency list

Frequently Asked Questions

Can "mm" and "MP4" be used interchangeably?

No - they are not even the same part of speech. "mm" is a symbol and "MP4" a name, so a sentence built for one is usually ungrammatical with the other.

Which is more common, "mm" or "MP4"?

"mm" is the more common of the two: it sits at frequency rank #1,092 in our French list, against #49,242 for "MP4". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

Remembering mm vs MP4

The fastest way to pick the right one every time.

Check the role first: if you need a symbol, it's “mm”; for a name, it's “MP4”.
See each word in full, definition, IPA, etymology and its other confusables. Full “mm” entry
Browse more pairs most likely to be confused. Most confusable