A decade is a period of ten years. The word is derived from the late Latin decas, from Greek decas, from deca. The other words for spans of years also come from Latin: lustrum (5 years), century (100 years), millennium (1000 years). The term usually refers to a period of ten years starting at a multiple of ten. For example, "the 1950s" refers to 1950 through to 1959 (inclusive). In English, "decade" can also be used to specify any period of ten years. For example, "During his last decade, Mozart explored chromatic harmony to a degree rare at the time".
