Here's why:
* Short vowels are typically found in closed syllables (a syllable that ends in a consonant).
* Closed syllables usually have a short vowel sound. For example, in the word "cat", the vowel "a" is short because the syllable "cat" ends in the consonant "t".
In "boy", the vowel "o" is in an open syllable ("boy"). Open syllables end in a vowel. Open syllables typically have long vowel sounds. In "boy", the "o" makes a long vowel sound, similar to the "o" in "go".
Therefore, "boy" is not a short vowel word.