Here's why:
* Short vowel sounds are typically quick and sharp. They are often represented by the vowel letter alone (e.g., "i" in "shiver").
* Long vowel sounds are typically drawn out and can often be represented by a vowel followed by a silent "e" (e.g., "bite", "cone").
The "i" in "shiver" makes a short vowel sound similar to the "i" in "pin" or "hit".