person in charge; manager; chief; head
Refers to the person responsible for a task, project, or group. Often used in workplace or organizational contexts.
The person in charge of this project is Mr. Tanaka.
Please check with the person in charge.
担当者 is the person assigned to handle a particular matter, often used for specific duties, whereas 主任者 implies a higher-level supervisory role.
Compound of 主任 (shunin, 'person in charge') + 者 (sha, 'person'). The exact historical derivation is uncertain, but the word follows a common pattern for occupational titles.