Duration: Amount of time. "The total duration of the flight is two hours."
1) Term: a word or phrase used to describe a thing or to express a concept.
"Financial integration" is a term commonly used in business
2) Term: A period of time (2 -6 months) / semester
The first term in school starts from 27 January to 24 March
Period: a length or portion of time.
Puberty is the period when a child starts maturing biologically, physically and mentally.