godan verb (-su)
join together; combine; unite; mix; sum up; agree with
Broadly means to bring things together into one. Can refer to physical joining, combining elements, summing numbers, or harmonizing opinions. Less common than 合わせる (あわせる) in modern speech; often appears in formal or written contexts. The gloss 'to agree with' is used when opinions or plans come together.
See also: 合する
They combined the technologies of both companies to develop a new product.
二人の意見が合して、計画はスムーズに進んだ。
Their opinions agreed, and the plan proceeded smoothly.