Discussion of textile fiber classifications with respect to length of the fiber (staple fibers, filament fibers) and origin of the fiber (natural fibers, synthetic or man made fibers, regenerated fibers).
There can be several possibilities: 1. Yes, filament fibers can be used as filament yarns according to desired denier 2. Filaments can be used in core of a spun yarn to make core spun yarns 3. one filament can be used in combination with another filament such as air covered yarn used in many ladies and mens clothing. For example polyester filaments can be air covered with viscose filaments or polyester/anyother filaments can be covered with elastane filament. Mostly these are multifilaments for a particular denier.