The English vowels are A, E, I, O, & U. (Sometimes Y is a vowel, pronounced as if it were I, and sometimes W substitutes for U.) Each can be pronounced in several ways.This page explains when each sound is commonly used.
(It's also available now as a 4-page pdf to download and print, as requested in the page comments.)
The most common sound for each vowel is its “short” sound:
(The International Phonetic Alphabet symbol for each sound is inside the backslashes://. You do not need to understand the IPA symbols; just look for an example word you know how to pronounce. For those who want more, this Wikipedia article gives a fairly simple demonstration of the IPA as used in English, with links to more detailed information.)
When syllables end in a vowel and then consonant (as in the examples above), the vowel is usually short. If there is more than one consonant, the vowel is almost always short.
This becomes important as a way to keep the same vowel sound when adding -ed to put a verb into the past tense. We often double an ending consonant to keep a short vowel short. For example, the past tense of 'stop' is 'stopped.' Otherwise the silent 'e' rule below (which also applies when followed by 'd') would give it a long 'o' sound like soap or hope. See the Simple Past Tense explanation of spelling changes.
The alphabet sounds (when the vowel “says its name”) are called “long vowels.”
We call them ‘long’ because we hold them longer than the short sounds, but they are completely different sounds-- not a longer version of the same sound.
Silent ‘E’ Rule: When a vowel and consonant are followed by an ‘e’, the ‘e’ is almost always silent, but it causes the preceding vowel to be long. (Examples: ate, plane, Pete, bite, nine, rope, note, cube, flute.)
Other Long Vowels: A vowel at the end of a syllable is almost always long. Examples: I, we, he, she, go, try, potato and tomato.(Some English speakers use a short ‘a’ in the 2nd syllable, while others use a long ‘a,’ but both ‘o’s are long for everyone.)
-Igh and -ight are usually long I (and silent GH): bright, fight, high, light, might, night, right, sigh, sight, tight.
Often the first letter of the vowel combinations, especially ‘ai’, ‘ay’, ‘ea’ (sometimes-- see Digraphs, below), ‘ee’, & ‘oa,’ will be long & the second will be silent. (An old rhyme for children says “when 2 vowels go walking, the first does the talking.”) So ’plain’ sounds just like ‘plane,' ‘meat’ and ‘meet’ like ‘mete,’ etc.
However, there are many exceptions. (See the link to English Vowel Digraphs, at the bottom of this page, for the most common ones.)
These contrasts demonstrate the rules (in each column, first short, then long):
Besides the long and short sounds, there are other vowel sounds.
Any vowel in an unaccented syllable has a neutral or“schwa”/ə/ sound: Examples: the ‘a’ in above, or approve, the ‘e’ in accident, camera or mathematics, the ‘i’ in family or officer, the ‘o’ in freedom or purpose, or the ‘u’ in industry or succeed.
if a vowel is followed by R, it changes in quality, and is neither long nor short. (ER, IR, and UR are often -- though not always--the same sound.)
Examples with phonetic symbols:
Sometimes in English a vowel is pronounced with a sound that usually goes with a different letter. For example, in my California dialect, the ‘a’ in ‘father’ or ‘want’ is pronounced very much like the ‘au’ in ‘audio’ or the short ‘o’ in ‘pot’ or ‘hot.’ That’s not true for all English speakers, however. Also, some common words use ‘o’ for a short ‘u’ sound: of, love, money, other, some, son.
(For the exact pronunciation of any word, consult a good dictionary. Most list the sound symbols they use on one of the front pages.)
See ESL Phonics for examples of the most common pronunciations of consonants as well as vowels, including 'Y' used as either a vowel or a consonant. (See also Consonant Digraph Sounds for pronouncing combinations of consonants.)
Because English has adopted words (and often some of their sounds), from so many other languages, none of these rules is always true. However, these English vowel rules will help you guess at the pronunciation of words you read. For that reason they may also help you guess their meaning, if you have heard them but not read them before. They should also help make English spelling a little easier.
P.S. A great way to learn how to pronounce English words and practice listening and reading comprehension at the same time is with podcasts or videos that provide transcripts (so you can read along as you listen.)
Check out Listening and Reading Comprehension Exercises for some at various levels with quizzes to check your understanding afterward. There are many other good sites for this too. One of the easiest for beginners or low intermediate English students is Voice of America (news-- and lots more!).