The Letter 'U' in Spanish 

The letter 'u' represents the close rounded vowel /u/ in Spanish which is like the English 'u' in words like "rude" but shorter. Its pronunciation is unaffected by its position in the word and its length is stable. Here are some examples:

When 'u' comes between the consonants 'g' or 'q' and the vowels 'e' or 'i' – that is, in combinations like 'que', 'qui', 'gue', and 'gui' – it is not pronounced. For example:

There are cases, however, where the 'u' between 'g' (but not 'q') and 'e' or 'i' should not be silent. In these cases, a diaeresis mark (¨) appears above 'u' which shows that it must be pronounced. In these words, the pronunciation of 'u' is affected by the formation of diphthong (see below), which causes it to be pronounced as a gliding /w/. Here are some examples:

When 'u' is used next to another vowel (/a/, /e/, /o/, and /i/), it forms a diphthong and is pronounced as a gliding semivowel /w/. Here are some examples:

However, when the 'u' next to another vowel is stressed (ú), a diphthong break occurs; which means each vowel is pronounced separately and 'u' keeps its original /u/ pronunciation. For example: