noun, noun, used as a prefix
together with; jointly; co-
Used as a noun-like element or prefix meaning that people or things act, exist, or are involved together. Often appears inside compounds rather than as a free standalone noun.
共働きの家庭が増えている。
The number of households where both partners work is increasing.
友人と共に旅行した。
I traveled together with a friend.
noun, noun, used as a prefix
A limited prefix-like use meaning the same or matching item, material, or kind; common in compounds such as 共布, “matching/same cloth.”
このワンピースには共布のベルトが付いている。
This dress comes with a belt made of the same fabric.
suffix
Suffix after a number, group word, or pronoun-like expression, meaning all members of the set. With a negative predicate it means none of them or neither of them.
兄弟二人とも医者です。
Both brothers are doctors.
学生は三人とも来なかった。
None of the three students came.
suffix
including; inclusive of
Suffix used to say that a stated amount or item is included, often in prices, charges, or set expressions. This use is narrower and somewhat written or transactional compared with 込み.
代金は送料ともで三千円です。
The price is 3,000 yen including shipping.
A normal adverbial expression for “together”; 共 is shorter and often bound in compounds or fixed written expressions.
Means “both” as a noun or pronoun. The suffix とも attaches to a set expression, as in 二人とも, and can also mean “none” with a negative predicate.
A common everyday way to say a price or amount includes something, as in 税込み. とも in the “including” sense is more limited and often appears in set price expressions.
A native Japanese reading とも conventionally written with 共, a kanji associated with togetherness and shared involvement. The exact historical derivation of the Japanese word is uncertain.