demonstrative (adj.)

late 14c., demonstratif, "characterized by logic, based on logic, showing or making manifest the truth or existence (of something)," from Old French démonstratif (14c.) and directly from Latin demonstrativus "pointing out, demonstrating," from demonstrat-, past-participle stem of demonstrare "to indicate, describe" (see demonstration).

The grammatical sense, "pointing out the thing referred to," is from mid-15c.; general sense of "having the quality of clearly showing, illustrative" is by 1520s. Meaning "given to or characterized by strong outward expressions of feelings" is from 1819. Related: Demonstratively; demonstrativeness.

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Definitions of demonstrative from WordNet
demonstrative (adj.)
given to or marked by the open expression of emotion;
an affectionate and demonstrative family
demonstrative (adj.)
serving to demonstrate;
Synonyms: illustrative
demonstrative (n.)
a pronoun that points out an intended referent;
Synonyms: demonstrative pronoun