Here's why:
* Short vowel sounds are typically represented by a single vowel letter in a word, and the vowel sound is short and quick. In "yellow," the "e" is followed by a consonant ("l") and another vowel ("o"). This creates a short "e" sound.
* Long vowel sounds are usually represented by a vowel followed by a silent "e" at the end of the word, or by a vowel digraph (two vowels together).
Let me know if you'd like to explore more examples of long and short vowels!