Is grass a sort vowel sound?

The word "grass" doesn't have a vowel sound. It's a bit tricky because we think of the "a" as a vowel, but in this case, it's a diphthong.

A diphthong is a combination of two vowel sounds that blend together. In "grass," the "a" sound actually combines with a short "e" sound, making it a diphthong rather than a simple vowel sound.

This is why it's pronounced "græs" with a slightly longer "a" sound, not "gras" with a short "a" sound.