英语中有26个字母，其中字母a、e、i、o、u是元音字母，其余21个是辅音字母，其中y字母有时作元音字母用。下面是关于元音字母和辅音字母的实例。
The vowels of the alphabet, I know their letter names, oh,
A, e, i, o, u, a, e, i, o, u,
A, e, i, o, u and sometimes y.
We know that, in English, letters represent sounds. The letters a, e, i, o, and u are used alone or in combination with each other to represent vowel sounds. So, for the sake of simplicity, we call those letters vowels. Letters and sounds are not the same thing, though. So, if we're talking about y, then we really need to know if we're talking about the letter y or the y sound. This is because the letter y sometimes represents a vowel sound and sometimes represents a consonant sound. The confusion occurs because the y sound is generally considered to be a consonant sound. This is for two reasons.
First, consonant sounds are created with a more restricted vocal tract than vowel sounds. During the y sound, the the tongue is held slightly closer to the tooth ridge during the y sound than for the vowel sound most similar to it: the long e sound. This can be heard, though it is very slight, in the minimal pair yeast/east. At the beginning of the word yeast, y-e-a-s-t, my tongue is close enough to my tooth ridge for the airflow to be considered restricted. My vocal tract is not as constricted in the beginning of the word east e-a-s-t. Listen to both words again: yeast/east. The trouble with the constricted vocal tract explanation is that there is no exact amount of constriction that classifies a sound as a consonant or a vowel.
Therefore, we rely more on the second characteristic of determining whether a sound is a vowel or consonant: all vowels must create a syllable. The words yeast and east are both only one syllable in length. They both contain only one vowel sound, the long e. The means that the y sound cannot be a vowel. If it were a vowel, the word yeast, beginning with a y sound, would be two syllables in length.
Despite the fact that the y sound is a consonant sound, there are many, many more words that use the letter y to represent a vowel sound than use the letter y to represent a consonant sound. To add more confusion, let's remember that the letter y commonly used in creating at least four different vowel sounds: the long a, long i, short i, and oi sound.
Of those four sounds, probably, the most common vowel sound created with the y spelling is the short i sound at the end of a word whose last syllable is unstressed (as in the words happy and pony). It represents the long i sound, both at the end of a word whose last syllable is stressed (as in the words shy and dry), or in the middle of a word (as in the words cycle and dynamic). The letter y mid-word can also represent the short i sound, as in the words myth and symbol.
Digraphs are sounds represented by two letters, and the letter y can be involved here, too. Remember that the ay spelling is commonly used for the long a sound (as in the words day and play), and the oy spelling of the oi sound (as in the words boy and joy).
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