The noun decrease has 4 senses (first 2 from tagged texts)
1. (7) decrease, lessening, drop-off -- (a change downward; "there was a decrease in his temperature as the fever subsided"; "there was a sharp drop-off in sales")
2. (1) decrease, decrement -- (a process of becoming smaller or shorter)
3. decrease, decrement -- (the amount by which something decreases)
4. decrease, diminution, reduction, step-down -- (the act of decreasing or reducing something)
Overview of verb decrease
The verb decrease has 2 senses (first 2 from tagged texts)
1. (23) decrease, diminish, lessen, fall -- (decrease in size, extent, or range; "The amount of homework decreased towards the end of the semester"; "The cabin pressure fell dramatically"; "her weight fall to under a hundred pounds"; "his voice fell to a whisper")