Refers to a role, task, or obligation one is entrusted with, often in formal or organizational contexts. Common in compounds like 責任 (responsibility) and 任務 (mission).
He took up a new duty.
He is the right person for the duty.
I did my best to fulfill my responsibility.
He bears a heavy duty.
職務 refers concretely to the duties attached to one's job or post, while 任 is a more formal, abstract word for an entrusted responsibility.
使命 carries a sense of calling or mission with strong personal purpose, while 任 is a neutral, formal term for a duty one is given.
The kanji 任 originally depicts a person bearing a burden, conveying the idea of being entrusted with a task. The reading にん is the on'yomi, commonly used in compounds.
term of office; period of appointment
moving to a new post; proceeding to a new appointment
entrusting; delegation; authorization
successor; replacement
taking up a new post; assuming a new position
full-time; exclusive assignment; dedicated
resignation; stepping down; retirement
concurrent post; additional role; serving also as
predecessor; former incumbent
nomination; selection; appointment
first appointment; initial posting
standing; regular; permanent
trust; confidence; credence
newly appointed; new appointment; inaugural
successive appointments; consecutive posts
no confidence; non-confidence; lack of confidence
entrust entirely; leave completely to
competent; suitable; qualified
appoint; nominate · assume (responsibility); take on (a duty) · pose as; pretend to be
being in office; tenure
chivalry; chivalrous spirit; helping the weak and fighting the strong · yakuza (euphemistic)