The vowel system is the most complicated part of the pronunciation-spelling system of English, because each vowel letter represents three or four different vowel sounds. The letter “U” has three different sounds, but one thing that is unique about “U” is that it has two Long-vowel sounds.
The basic sounds of the English letter “U” are: Long-U-1, Long-U-2, and Short-u.
Long-U-1
The sound of Long-U-1 is the same as the name of the letter “U”. However, this long-vowel sound is a little bit unusual because Long-vowels usually have two parts, but Long-U-1 has three parts (in IPA: /yuw/). Some common words with this sound are: use / music / huge / cute / unite / cure / menu / fuel / human / argue.
Long-U-2
The second Long-U sound is almost the same as Long-U-1, except that it has only two parts (in IPA: /uw/). Some words with this sound are: true / flute / blue / June / spruce / tune / rule / tube / duty / include.
Short-u
Short-u is pronounced in the center (not front, not back) middle (not high, not low) part of the mouth, and the tongue needs to be relaxed. Some common words with this sound are: up / just / but / much / under / us / run / study / number / because.
Schwa
Any vowel letter can use the schwa sound in unstressed syllables. However, since the schwa sound and Short-u are both made in the same place in the mouth, they end up sounding the same. A linguist would make a distinction between Schwa and Short-u based on stress, so for example, the first letter of the word “under” would be considered a Short-u sound, but in the word “upset” the first letter would be called a Schwa. The good news for learners of English is, you can treat them as the same sound, and your English pronunciation will sound great.
So remember, it is very rare to find the letter “U” pronounced with something other than these three basic sounds. There is a handful of words with a “U” pronounced as Short-oo: sugar / put / push / puss / pull / full / bull / cushion. There are also two words with a very unusual pronunciation, “busy” and “business”. In these two words the “U” has a Short-i sound! Otherwise, when you see the letter “U” in a word, it will almost always have the sound of either Long-U-1, Long-U-2, or Short-u (Schwa).
ADDITIONAL NOTES
1. Vowel pair “OU” — Several different vowel sounds are used for the vowel pair “OU”, and it is not easy to predict. See: OU – Oh no!
2. Test yourself! — Many students have difficulty distinguishing between Short-u and Short-o. You can test yourself on the “Vowel Test” page of the PronunciationCoach site.
PronunciationCoach 
the word ‘bury’ also has letter ‘u’ that produces short /e/ sound.
Good catch!
I really like it
Why do English teachers in Spain insist on pronouncing the U as an A eg: bas (bus) pab (pub) fanny (funny) Tramp (Trump), cat (cut) I have many discussions with English learners in Spain about this and try to explain that the words they are saying have different meanings, as in cat, Tramp etc , but they wont listen !!
They never say Bal for bull or pal for pull
This is a common issue for Spanish speakers because Spanish does not have a vowel that is equivalent to English Short-u. It is part of a prototypical Spanish-accent in English. The post “Boss or Bus?” covers the difference between the two vowels. https://pronunciationcoach.blog/2012/02/21/boss-or-bus/
The words “bull” and “pull” have Short-oo, like “bush”, “book”, “push”, “put”, and “sugar”. (You can hear the distinction more easily with the words “put” and “putt”.)
Hi, just found your your site on long u. I would like to ask a question. The LongU2 sound is the same as Long OO ya?
Yes!! Long-OO, such as “moon”, “school” and “choose” is the same as the Long-U2 of “rule”, “clue”, and “true”.
I have a newer post with the sounds of Long-U in case you are interested:
the word busy has a short i sound
Yes! The word “busy” is an oddball that needs to be memorized. The word “business” also has a Short-i sound for the “U”.
What sounds letter u produces in these words: quick, quit and queen.
This is a special pair. The letter “Q” always goes with “U” and together they sound like “KW”.
This is helpful.
It recently occurred to me that the word ‘business’ is pretty unusual. The ‘u’ is pronounced like a long i, and the i isn’t pronounced. Are there any other words where the u is pronounced as an i? And what’s with that silent, standalone, should-be-pronounced i?
The word “business” is very unusual. The “U” in both “busy” and “business” sounds like Short-i!! These are oddballs that need to be memorized.
The missing middle syllable of “business” is less strange, because there are other words that have a missing middle vowel, which is what I talk about in the topic “Vanishing Syllables” https://pronunciationcoach.blog/2011/12/07/vanishing-syllables/
Wow i didn’t know that thanks for sayng and performing it
is the ü the same as a long u?
Perhaps. It depends on which dictionary you are using. Different dictionaries have devised their own systems for representing all of the different vowel sounds of English, so I would not be surprised that one of them has chosen to use that symbol.