The Collaborative International Dictionary of English v.0.48:

Identity \I*den"ti*ty\, n.; pl. Identities. [F. identit['e],
   LL. identitas, fr. L. idem the same, from the root of is he,
   that; cf. Skr. idam this. Cf. Item.]
   1. The state or quality of being identical, or the same;
      sameness.
      [1913 Webster]

            Identity is a relation between our cognitions of a
            thing, not between things themselves. --Sir W.
                                                  Hamilton.
      [1913 Webster]

   2. The condition of being the same with something described
      or asserted, or of possessing a character claimed; as, to
      establish the identity of stolen goods.
      [1913 Webster]

   3. (Math.) An identical equation.
      [1913 Webster]

WordNet (r) 3.0 (2006):

identity
    n 1: the distinct personality of an individual regarded as a
         persisting entity; "you can lose your identity when you
         join the army" [syn: identity, personal identity,
         individuality]
    2: the individual characteristics by which a thing or person is
       recognized or known; "geneticists only recently discovered
       the identity of the gene that causes it"; "it was too dark to
       determine his identity"; "she guessed the identity of his
       lover"
    3: an operator that leaves unchanged the element on which it
       operates; "the identity under numerical multiplication is 1"
       [syn: identity, identity element, identity operator]
    4: exact sameness; "they shared an identity of interests" [syn:
       identity, identicalness, indistinguishability]

Moby Thesaurus II by Grady Ward, 1.0:

146 Moby Thesaurus words for "identity":
   accord, accordance, affinity, agape, agreement, alikeness,
   alliance, amity, analogy, aping, approach, approximation,
   assimilation, balance, bonds of harmony, brotherly love, caritas,
   cement of friendship, charity, closeness, coequality, coextension,
   combination, communion, community, community of interests,
   comparability, comparison, compatibility, concord, concordance,
   conformity, congeniality, congruence, copying, correspondence,
   credo, creed, differentiation, differentness, distinctiveness,
   egohood, empathy, equality, equation, equilibrium, equipoise,
   equipollence, equiponderance, equity, equivalence, equivalency,
   esprit, esprit de corps, evenness, feeling of identity,
   fellow feeling, fellowship, frictionlessness, fusion, good vibes,
   good vibrations, happy family, harmony, human factor, ideology,
   imitation, indistinguishability, individualism, individuality,
   indivisibility, intactness, integrality, integration, integrity,
   inviolability, irreducibility, justice, kinship, levelness,
   like-mindedness, likeness, likening, love, metaphor, mimicking,
   mutuality, nearness, nominalism, nonconformity, oneness,
   organic unity, outlook, par, parallelism, parity, particularism,
   particularity, peace, personal equation, personal identity,
   personality, personship, philosophy, poise, proportion, purity,
   rapport, rapprochement, reciprocity, resemblance, sameness,
   self-identity, selfhood, selfness, selfsameness, semblance,
   sharing, similarity, simile, similitude, simplicity, simulation,
   singleness, singularity, solidarity, solidification, solidity,
   soul, symmetry, sympathy, symphony, team spirit, unanimity,
   understanding, undividedness, unification, uniformity, union,
   uniqueness, unison, unity, univocity, view, weltanschauung,
   wholeness



Bouvier's Law Dictionary, Revised 6th Ed (1856):

IDENTITY, evidence. Sameness.
     2. It is frequently necessary to identify persons and things. In
criminal prosecutions, and in actions for torts and on contracts, it is
required to be proved that the defendants have in criminal actions, and for
injuries, been guilty of the crime or injury charged; and in an action on a
contract, that the defendant was a party to it. Sometimes, too, a party who
has been absent, and who appears to claim an inheritance, must prove his
identity and, not unfrequently, the body of a person which has been found
dead must be identified: cases occur when the body is much disfigured, and,
at other times, there is nothing left but the skeleton. Cases of
considerable difficulty arise, in consequence of the omission to take
particular notice; 2 Stark. Car. 239 Ryan's Med. Jur. 301; and in
consequence of the great resemblance of two persons. 1 Hall's Am. Law Journ.
70; 1 Beck's Med. Jur. 509; 1 Paris, Med. Jur, 222; 3 Id. 143; Trail. Med.
Jur. 33; Fodere, Med. Leg. ch. 2, tome 1, p. 78-139.
     3. In cases of larceny, trover, replevin, and the like, the things in
dispute must always be identified. Vide 4 Bl. Com. 396.
     4. M. Briand, in his Manuel Complet de Medicine Legale, 4eme partie,
ch. 1, gives rules for the discovery of particular marks, which an
individual may have had, and also the true color of the hair, although it
may have been artificially colored. He also gives some rules for the purpose
of discovering, from the appearance of a skeleton, the sex, the age, and the
height of the person when living, which he illustrates by various examples.
See, generally, 6 C. & P 677; 1 C. & M. 730; 3 Tyr. 806; Shelf. on Mar. &
Div. 226; 1 Hagg. Cons. R. 189; Best on Pres. Appx. case 4; Wills on
Circums. Ev. 143, et seq.