A general term for a person who works on a ship, often in a professional capacity. Slightly formal; in casual contexts 船乗り (ふなのり) is also common.
When he was young, he traveled the world as a sailor.
To become a seaman, specialized training is required.
seamen's union
Compound of 海 (sea) and 員 (member, personnel). The exact historical derivation is uncertain, but the word follows a common pattern for occupational terms.