Source : Webster's Revised Unabridged Dictionary (1913)

Mandatory \Man"da*to*ry\, a. [L. mandatorius.]
   Containing a command; preceptive; directory.

Mandatory \Man"da*to*ry\, n.
   Same as {Mandatary}.

Source : WordNet®

mandatory
     adj : required by rule; "in most schools physical education are
           compulsory"; "attendance is mandatory"; "required
           reading" [syn: {compulsory}, {required}]

mandatory
     n 1: the recipient of a mandate [syn: {mandatary}]
     2: a territory surrendered by Turkey or Germany after World War
        I and put under the tutelage of some other European power
        until they ar able to stand by themselves [syn: {mandate}]