A vowel sound is a type of speech sound produced when air flows freely through the mouth without any significant obstruction. In the English language, the primary vowel sounds are represented by the letters A, E, I, O, and U. Each of these letters can produce different sounds depending on their placement in a word and the letters surrounding them. Vowel sounds are essential for forming syllables and words. They can be classified into two categories: short and long vowel sounds. For example, the A in "cat" is a short vowel sound, while the A in "cake" is a long vowel sound. Understanding vowel sounds is crucial for proper pronunciation and reading skills.