Here's why:
* Short vowel sounds are typically quick and sharp. They are often found in words with one syllable and a closed syllable structure (ending in a consonant).
* Long vowel sounds are typically longer and more drawn-out. They are often found in words with two syllables or a vowel followed by a consonant and a silent "e."
In the word "slap," the vowel sound is short and quick. It's the same as the vowel sound in words like "cat," "hat," and "bat."