Culture: the ensemble of signs and signifying practices, with all their given meanings, of a group.

Ideology: beliefs, values, patterns of feeling, habits of thought through which we perceive, explain, and justify reality.  For example, social practices or arrangements that are said to be "natural" or "unnatural."

Discourse: a system of representation and meanings linked to a specific discipline, institution, practice, or pattern of belief, and that limits what can be expressed and understood.