Sŭb.

A Latin preposition, denoting under or below, used in English as a prefix, to express an inferior position or intention, and also a subordinate degree, or imperfect state of a quality. Before f, g, p, r, and m, the b is changed into those letters, as in suffer, suggest, suppose, surrogate, and summon.

When prefixed to the name of a chemical compound, sub denotes that this, if an oxysalt, contains a less number of equivalents of the acid than of the base, or that the base is a sub-oxide; or, if it is a haloid salt, or analogous compound, that the electro-negative is in a smaller proportion than the electro-positive constituent, or is combined with it in the smallest proportion possible; as in sub-bromide, sub-iodide, &c., haloid sub-salts containing a less number of equivalents of bromine, iodine, &c., than of the substance with which they are joined; sub-sulphide, a sulphide containing one equivalent of sulphur to two or more of the body with which it is compounded; and the like.