What is a continuous line of fibers twisted together known as?

The correct answer is that a continuous line of fibers twisted together is known as yarn. Yarn is made by spinning together various types of fibers, which can be natural (like cotton or wool) or synthetic (like polyester or nylon). This process results in a long, flexible strand that can be then used for a variety of purposes, including knitting, weaving, and sewing.

While thread, rope, and filament may initially seem related, they refer to different concepts. Thread is typically thinner and used for sewing, whereas rope consists of multiple strands twisted together, creating a much thicker and stronger material suitable for lifting and securing heavy loads. A filament, on the other hand, refers to a single, long continuous structure, which can be used in various applications but does not necessarily imply a twisted construction like in yarn.