numeral / noun
twelve
TWELV/twˈɛlv/
The number after eleven and before thirteen.
The carton holds twelve eggs in two rows of six.

Etymology
Old English twelf carries the original idea of “two left” over ten. The number is thus expressed as a remainder beyond ten rather than as one more than eleven.
In context
keep your chest high six seven soft bend in the standing leg nine ten eleven and twelve