b. If the root begins with any consonant except one of these three:—
But sometimes v is changed into b, or b itself is kept.
Before m or n, the prefix is contracted into ma-.
Ma- (or M- before vowels) is a shorter form of Man-, which forms a few transitive verbs, but a large number of adjectives usable as verbs.
Rules for the formation of the Imperative Mood of Active Verbs.
(1) Affix -a, unless the word already ends in a.
(2) Shift the accent one syllable forward, unless the root is a monosyllabic diphthong; or, unless the root is two-syllabic, but with the accent on the last syllable; or, unless the root is two-syllabic, but ending in -ka, -na, or tra-.
(3) Sometimes also one or other of the following changes are necessary:—
Change of a consonant preceding the final a: this occurs only in roots ending in -ka, -na, or -tra, where k becomes h or f, tr becomes t, r, or f, and n becomes m.