For each of the vowel letters of American English, what is the most commonly used sound of each of them. That is, what is the most commonly used sound that represents the letter "a", the most commonly used sound that represents the letter "e", etc.?
The mighty schwa is the most common vowel sound. Spelled in IPA like ə, transliterated as "uh", and generally sounds like a grunt-turned-vowel. Basically the easiest sound to make.
In English, schwa is the most common vowel sound. It is a reduced vowel in many unstressed syllables especially if syllabic consonants are not used. Depending on dialect, it may be written using any of the following letters:
- 'a', as in about [əˈbaʊt]
- 'e', as in taken [ˈtʰeɪkən]
- 'i', as in pencil [ˈpʰɛnsəl]
- 'o', as in memory [ˈmɛməri]
- 'u', as in supply [səˈplaɪ]
- 'y', as in sibyl [ˈsɪbəl]
- various combinations of letters, such as 'ai' in mountain [ˈmaʊntən]
- unwritten, as in rhythm [ˈɹɪðəm]
It's the "center" vowel on the IPA vowel diagram.
English spelling does not always nicely correspond to sounds, so pretty much any rule about it is going to be a rule of thumb. However, in elementary school, we were taught that every vowel has two sounds: a short sound and a long sound. The short sounds are found in words like "can", "bet", "fin", "con", and "cut". The long sounds are found in words like "cane", "beet", "fine", "cone", and "cute", and are also the names of the letters.
This also leads to the long-short pronunciation rule: a vowel is pronounced long if the consonant following it is followed by a vowel and short if it's followed by a consonant (or nothing). This is the reason behind the silent "e"s in the aforementioned words and the doubling of letters with certain suffixes ("pinning a ribbon" vs "pining for the fjords").
English vowel letters can be pronounced in all manner of ways depending on the word, but these long and short sounds are the most common.