sum vs sun: hear and say the difference
sum and sun are identical except for one sound: sum has the m sound, /m/, and sun has the n sound, /n/. Both hum through the nose; M closes the lips and does nothing with the tongue, N leaves the lips open and presses the tongue tip on the ridge.
The two words
The difference
What actually changes
Both hum through the nose; M closes the lips and does nothing with the tongue, N leaves the lips open and presses the tongue tip on the ridge.sum — /m/
- Lips
- Closed and relaxed.
- Tongue
- Low and free.
- Jaw
- Nearly closed.
sun — /n/
- Lips
- Open and relaxed.
- Tongue
- Tip pressed on the ridge behind the top teeth, sides sealed.
- Jaw
- Slightly open.
Each word in a sentence
sum
Check the sum at the bottom.
sun
The sun set behind the hill.
Why this pair is hard
Spanish has no word-final m, so 'sum' ends like 'sun'. French and Portuguese nasalise the vowel instead of closing the lips or touching the ridge, so both endings can disappear. Japanese has one syllable-final nasal that takes its shape from the next sound, so a final M can drift toward N.
Straight answers
What is the difference between "sum" and "sun"?
One sound. sum is /sʌm/ and sun is /sʌn/ — everything else in the two words is identical, so that single contrast carries the whole meaning. Both hum through the nose; M closes the lips and does nothing with the tongue, N leaves the lips open and presses the tongue tip on the ridge.
Why do I say "sum" and "sun" the same way?
Spanish has no word-final m, so 'sum' ends like 'sun'. French and Portuguese nasalise the vowel instead of closing the lips or touching the ridge, so both endings can disappear. Japanese has one syllable-final nasal that takes its shape from the next sound, so a final M can drift toward N.
Should I train my ear or my mouth first?
Your ear. If you cannot reliably hear which word was said, your mouth has no target to aim at, and drilling produces a sound you cannot check. Run the listening test on this page until you are scoring four or five out of five, then record the pair.
Say "sum" and "sun" and see which one you said
One take covers both words: reference mode aligns each sound against its target, so the contrast comes back scored on both sides. Free, private, in your browser.