Jersey
The basic single knit, used for t-shirts.
Jersey is a single knit: loops on one face, purl on the other. It stretches in one direction more than the other, and the edges curl — which is why hems are finished with a rib or a double fold.
Cotton jersey for t-shirts typically runs 130–240 gsm. Below 130 it becomes sheer; above 200 it reads as a heavyweight tee.