Aplanatic focus. (Opt.) See under Aplanatic. -- Conjugate focus (Opt.),
the focus for rays which have a sensible divergence, as from a near
object; -- so called because the positions of the object and its image
are interchangeable. -- Focus tube (Phys.), a vacuum tube for Rúntgen
rays in which the cathode rays are focused upon the anticathode, for
intensifying the effect. -- Principal, or Solar, focus (Opt.), the
focus for parallel rays.
Fo"cus (?), v. t. [imp. & p. p. Focused (?); p. pr. & vb. n. Focusing.]
To bring to a focus; to focalize; as, to focus a camera. R. Hunt.
Fod"der (fd"dr), n. [See 1st Fother.] A weight by which lead and some
other metals were formerly sold, in England, varying from 19Ω to 24
cwt.; a fother. [Obs.]
Fod"der, n. [AS. fdder, fddor, fodder (also sheath case), fr. fda food;
akin to D. voeder, OHG. fuotar, G. futter, Icel. fr, Sw. & Dan. foder.
√75. See Food and cf. Forage, Fur.] That which is fed out to
cattle horses, and sheep, as hay, cornstalks, vegetables, etc.
Fod"der, v. t. [imp. & p. p. Foddered (-drd); p. pr. & vb. n.
Foddering.] To feed, as cattle, with dry food or cut grass, etc.; to
furnish with hay, straw, oats, etc.
Fod"der*er (?), n. One who fodders cattle.
Fo"di*ent (?), a. [L. fodiens, p. pr. of fodere to dig.] Fitted for, or
pertaining to, digging.
Fo"di*ent (?), n. (Zoˆl.) One of the Fodientia.
Fo`di*en"ti*a (?), n. pl. [NL., fr. L. fodiens p. pr., digging.]
(Zoˆl.) A group of African edentates including the aard-vark.
Foe (f), n. [OE. fo, fa, AS. fh hostile; prob. akin to E. fiend.
√81. See Fiend, and cf. Feud a quarrel.]
1. One who entertains personal enmity, hatred, grudge, or malice,
against another; an enemy.
A man's foes shall be they of his own household.