Qamatz (קָמָץ), is a long A-Class vowel.

A contextual variant, with the same appearance, called qamatz ħatuf (or qamatz qatan, the little qamatz), is a short O-Class vowel.

represented by a horizontal line beneath the letter with a teardrop or do underneath it, sometimes merged and represented as a simple “T” shape.

The long A-Class qamatz sounds like the “o” in commit.

See: niqqud