deca- [DEK uh], dec-, deka-, dek-

(Greek: ten; a decimal prefix used in the international metric system for measurements)

In the metric [decimal] system, deka- is used to show whole units: ten [U.S.] and tenfold [U.K.]; 101 [10]. The metric symbol for deka- is da.

decathlon (s) (noun), decathlons (pl)
An athletic contest consisting of ten different track-and-field events and won by the contestant having the highest total score.

Related "metric" families: yotta; zetta; exa; peta; tera; giga; mega; kilo; hecto; deci; centi; milli; micro; nano; pico; femto; atto; zepto; yocto.