Fe´ral, a. Wild; not tamed. Opposed to domestic. The mallard is the feral stock of the tame duck.

Ferrugin´eous or Ferru´ginous, a. Rusty-red.

Fe´tus or Fœ´tus, n. Unborn young. (But the unhatched young of birds are oftener called embryos.)

Fibril´la, n.; pl. fibrillæ. Little fibre.

Fib´rin, a. Certain animal substance of fibrous composition, found in the blood and elsewhere.

Fi´bro-car´tilage, n. A kind of cartilage of fibrous structure, such as that between vertebræ and many other joints.

Fib´ula, n. Smaller outer leg-bone, lying alongside the tibia.

Fil´ament, n. Thread or slender fibre.

Filament´ous, Fil´iform, a. Threadlike; composed of filaments; oftener, very narrowly linear.

Filopluma´ceous, a. Having the structure of a filoplume.