Nylon monofilament — Extruded nylon: cheap, knots beautifully, floats slowly and stretches 20-30 % — a rubber band that keeps a topwater on top and has no business on any rig you feel or set.
Copolymer / fluoro-coated nylon — Nylon blends and nylon with a fluorocarbon skin, sold as "copolymer" or "hybrid": thinner and stiffer than plain nylon, still a nylon in everything that matters — stretch, absorption, visibility.
Ester line (polyester monofilament) — A polyester monofilament from Japanese light-game fishing: sinks, stretches only 5-8 %, thin and sensitive as braid, brittle as glass on a shock — the ultralight main line that most North American anglers have never seen.
Wire leader (steel / titanium) — Steel or titanium leader for teeth: single-strand, seven-strand or knottable titanium in 20-45 cm — the only line pike and muskie cannot cut, and dead weight on a bass rig.
Titanium-alloy leader — Single- and multi-strand versions exist. Alloy and construction set flexibility; not all are pure titanium.