1. Characterizing two things that contain or produce a difference or distinction: Both of the colors used in the painting certainly have a contrastive effect making it very bright and gay.
2. Pertaining to related words that are at variance with each other: There are many contrastive words, such as "rich" and "poor", "tall" and "short", or "big" and "small" whereby each pair has an opposite meaning.
3. Regarding the comparison between elements of a sentence or between sentences: Such terms as "though", "but", or "or" are conjunctions which have a contrastive purpose or usage and are helpful when needed in explaining topics.