The Collaborative International Dictionary of English v.0.48:
Lemon \Lem"on\ (l[e^]m"[u^]n), n. [F. limon, Per. l[imac]m[=u]n;
cf. Ar. laim[=u]n, Sp. limon, It. limone. Cf. Lime a
1. (Bot.) An oval or roundish fruit resembling the orange,
and containing a pulp usually intensely acid. It is
produced by a tropical tree of the genus Citrus, the
common fruit known in commerce being that of the species
Citrus Limonum or Citrus Medica (var. Limonum). There
are many varieties of the fruit, some of which are sweet.
2. The tree which bears lemons; the lemon tree.
Lemon grass (Bot.), a fragrant East Indian grass
(Andropogon Sh[oe]nanthus, and perhaps other allied
species), which yields the grass oil used in perfumery.
Lemon sole (Zool.), a yellow European sole (Solea
Salts of lemon (Chem.), a white crystalline substance,
inappropriately named, as it consists of an acid potassium
oxalate and contains no citric acid, which is the
characteristic acid of lemon; -- called also salts of
sorrel. It is used in removing ink stains. See Oxalic
acid, under Oxalic. [Colloq.]