The short vowel sounds for the five vowels in the English language are a as in cat, e as in pet, i as in sit, o as in dog and u as in bug. The letter y used as a vowel makes the short i sound, as in mystic.
Short vowel sounds appear frequently in beginning reading programs because short, recognizable three letter words with the vowel in between two consonants produce the short vowel sound. Examples of the pattern include the words hat, bat, mat and sat. Teaching children to recognize this pattern as a guide to pronunciation is the key to using phonics to decode text, according to Brainpop.
The long vowel sound is produced by saying the name of each vowel. In the word peek, the long e vowel sound is the same as the name of the letter. Saying the name of each of the other vowels produces the long vowel sound according to Udemy.
Marks placed above a vowel to indicate whether the vowel is long or short are called diacritical marks. A straight line above a vowel indicates is it a long vowel and a u-shaped mark indicates that it is a short vowel, according to Phonics on the Web.