duty, war, campaign, drafted labor, office, service, role
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役 centers on a person being assigned a task or function: a duty, role, or service. The war and campaign senses are specific historical applications of being drafted into military service.
role; assignment; responsibility; duty; function; job; service
part; assigning (allotment of) parts; role; duties
active duty; active service
to be useful; to be helpful; to serve the purpose
company director; board member
director; executive
leading part; leading actor; leading actress
to be helpful; to be useful
actor; actress
duty; role; function
municipal office; council; city hall
government office; public office
government official
penal servitude; imprisonment with hard labor (hard labour)
villain; baddie; the villain's part
post; official position
child actor; child actress
substitute (actor); stand-in; fill-in; understudy; double
retiring from military service
town hall
military service; conscription
(company) director; executive; top management
penal servitude; serving time in prison
supporting role (actor); minor role
役 combines 彳 (movement, going) with 殳 (a hand holding a weapon or tool), suggesting a person sent out to perform a task or service. The modern form preserves this general idea of assigned action.
The left side 彳 suggests a person on the move, and the right side 殳 looks like a hand holding a tool. Picture someone being sent out with a tool to do their assigned duty or role.
For ヤク, imagine a yak carrying a heavy load of duties: yak -> ヤク, and the yak is performing its service.