focus

(fo’kus), pl. fo’ci (L. “ fire-place "J. 1. The point of convergence of light-rays or of the waves of sound. 2. The chief center of a morbid proce . aplanatic f., that focus or point from which rays diverging pa the lens without spheric aberration. conjugate f., the point at which rays that come from some definite point are brought together. principal f., the point at which rays that were parallel before refraction are brought together. f., the point at which convergent rays inter- sect. virtual f., the point at which divergent rays would intersect if prolonged backward. Poniculum (fe-nik’u-lum), gen. fenic’uli [L.J. A genus of umbelliferous plants: the fruit of F. vudga’re, the common fennel, is carminative, aromatic, and stimulant.