가요 (a well known song released by a professional singer - slightly formal) 노래 (any type of song)
단추 - 버튼 = same meaning and usage. 단추 is much more common as a Korean naive word; 버튼 is English.
그릇 (bowl - has a deep, hollow shape) - 접시 (plate - has a flat shape)
데 (a place) 위치 (a location of something relative to the others) - 데 is like 곳, but has special idiomatic uses.
불만 (sentiment of dissatisfaction, complaint) 불편 (inconvenience)
상품 ((commercial product, merchandise) 제품 (manufactured product) - similar with a different focus.
<s>시인</s> => 신인 (newcomer in a (entertainment) sector) - 신입 (new recruit/employee/member). 시인 = poet.
* Both are often used like a prefix: 신인 가수/배우 (new singer/actor), 신입 사원/회원 (new employee/member). * * 신인 is a free player in a sector, while 신입 belongs to a rigid organization or group.