Thread:

Good old fashioned genuine silk
Polyester
Nylon
Kevlar

Discussion:

Size: diameter/denier

Denier : The denier value is defined as the mass in grams per 9000 meters of yarn

table of comparison of threads, thicknesses, denier, breakstrain:

http://surreyflydresser.org.uk/surreyflydresser/docs/Thread_Comparison_Chart.pdf