Source : Webster's Revised Unabridged Dictionary (1913)

Attentive \At*ten"tive\ ([a^]t*t[e^]n"t[i^]v), a. [Cf. F.
   attentif.]
   1. Heedful; intent; observant; regarding with care or
      attention.

   Note: Attentive is applied to the senses of hearing and
         seeing, as, an attentive ear or eye; to the application
         of the mind, as in contemplation; or to the application
         of the mind, in every possible sense, as when a person
         is attentive to the words, and to the manner and
         matter, of a speaker at the same time.

   2. Heedful of the comfort of others; courteous.

   Syn: Heedful; intent; observant; mindful; regardful;
        circumspect; watchful. -- {At*ten"tive*ly}, adv. --
        {At*ten"tive*ness}, n.

Source : WordNet®

attentiveness
     n 1: paying particular notice (as to children or helpless
          people); "his attentiveness to her wishes"; "he spends
          without heed to the consequences" [syn: {heed}, {regard},
           {paying attention}] [ant: {inattentiveness}]
     2: the trait of being considerate and thoughtful of others
     3: the trait of being observant and paying attention [ant: {inattentiveness}]