1. [n]  a mood (as in Greek or Sanskrit) that expresses a wish or hope; expressed in English by modal verbs
2. [adj]  (grammar) relating to a mood of verbs in some languages; "optative verb endings"
3. [adj]  indicating an option or wish

OPTATIVE is a 8 letter word that starts with O.

1. \Op"ta*tive\, a. [L. optativus: cf. F. optatif.]
   Expressing desire or wish. --Fuller.
   
   {Optative mood} (Gram.), that mood or form of a verb, as in
      Greek, Sanskrit, etc., in which a wish or desire is
      expressed.
   
   

2. \Op"ta*tive\, n. [Cf. F. optatif.]
   1. Something to be desired. [R.] --Bacon.
   
   2. (Gram.) The optative mood; also, a verb in the optative
      mood.