10 (ten) is theevennatural number following9 and preceding11. Ten is the base of thedecimal numeral system, the most common system of denotingnumbers in both spoken and written language.
The number "ten" originates from theProto-Germanic root "*tehun", which in turn comes from theProto-Indo-European root "*dekm-", meaning "ten". This root is the source of similar words for "ten" in many otherGermanic languages, likeDutch,German, andSwedish. The use of thedecimal system is probably because humans have tenfingers and tentoes, which people may have used to count by.
A collection of ten items (most often ten years) is called adecade.
Theordinal adjective isdecimal; the distributive adjective isdenary.
Increasing a quantity by oneorder of magnitude is most widely understood to mean multiplying the quantity by ten.
To reduce something by one tenth is todecimate. (In ancient Rome, the killing of one in ten soldiers in a cohort was the punishment for cowardice or mutiny; or, one-tenth of the able-bodied men in a village as a form of retribution, thus causing a labor shortage and threat of starvation in agrarian societies.)
