资料来源 : Webster's Revised Unabridged Dictionary (1913)

Requisite \Req"ui*site\, a. [L. requisitus, p. p. requirere;
   pref. re- re- + quaerere to ask. See {Require}.]
   Required by the nature of things, or by circumstances; ??
   needful that it can not be dispensed with; necessary
   indispensable.

         All truth requisite for men to know.     --Milton.

   Syn: Necessary; needful; indispensable; essential. --
        {Req"ui*site*ly}, adv. -- {Req"ui*site*ness}, n.

资料来源 : WordNet®

requisiteness
     n : the state of being absolutely required