1The joining of two or more organizations or things into one — used for company mergers, joint events, and the like.
二つの労働組合が合同して一つの組織になった。
The two labor unions merged and became a single organization.
来月、両校の合同文化祭が開かれる。
Next month, a joint cultural festival between the two schools will be held.
「合同会社」は日本の会社形態の一つだ。
A "gōdō kaisha" (合同会社) is one type of company structure in Japan.
二社は業務提携から合同へと発展した。
The two companies developed from a business partnership into a full merger.
2Describing something done jointly by multiple parties — used as "合同の〜" or "合同で〜."
近隣の学校と合同で避難訓練を実施した。
We conducted a joint evacuation drill with a nearby school.
合同記者会見で両社の代表が説明した。
Representatives from both companies gave explanations at a joint press conference.
二つの部活が合同で練習試合をした。
The two club teams held a joint practice match.
3In mathematics, the property of two figures being identical in shape and size, or (in a congruence relation) being equal under a given modulus.
二つの三角形が合同であることを証明する問題が出た。
A problem asking to prove that two triangles are congruent came up.
合同な図形は対応する辺と角がすべて等しい。
Congruent figures have all corresponding sides and angles equal.