Equity is the state or quality of being fair. In classrooms, it's important to establish equity as any hint of unfairness turns everyone against the teacher.
In finance, equity refers to the value of a business or piece of property after subtracting the amount of the mortgage. Also in finance, equities are stocks, in contrast to bonds. Equity is from Middle English equite, from Old French équité, from Latin aequitas "equality," from aequus "equal."