decrease (Noun) — A change downward. ex. "there was a decrease in his temperature as the fever subsided"
decrease (Noun) — A process of becoming smaller or shorter.
decrease (Noun) — The amount by which something decreases.
decrease (Noun) — The act of decreasing or reducing something.
decrease (Verb) — Become smaller or less in size, extent, or range. ex. "The amount of homework decreased towards the end of the semester"
decrease (Verb) — Make smaller. ex. "He decreased his staff"