T-Shirt type fabric?

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hello all, does anybody know the proper name for t-shirt kinda fabric? i've searched for ages online but they all have crazy names and i have no idea what they mean in terms of REAL THINGS. what sort of terms would i be looking for? i'm particularly after some of the thinner stretchy type material, like girly tshirts are made of, rather than the thicker stuff blokes ones are made from.
arrgh i hope this makes sense! and thanks in advance for help :)