noun

• (uncountable) The act, process, or state of reinforcing or being reinforced.
• (countable) A thing that reinforces.
• (in the plural) Additional troops or materiel sent to support a military action.
• (uncountable, behavioral psychology) The process whereby a behavior with desirable consequences comes to be repeated.
• A small round white sticker placed around a punched hole in a piece of paper to prevent the binder's rings from tearing through the paper.