There are several types of yarn, classified based on their fiber content, texture, and production process. Some common types of yarn include:

Given the name, the most compelling direction combines the two meanings of the word: ("spinning a yarn") and connection (the physical thread).

Then there is the geometry. A knitted fabric is not woven; it has no warp and weft. Instead, it is a series of interconnected coils. This is why a knitted scarf can stretch 200% of its length and snap back. This "memory" is why early space suits had knitted "constant-wear" layers and why surgeons use knitted vascular grafts—they stretch and pulse with the body.