GRAMMAR DETAIL

と

with; together with

Marks the other party involved with a verb expressing exchange, cooperation, opposition, or another reciprocal relationship.

Examples

同僚と意見を交換した。

I exchanged opinions with a coworker.

私は姉と同じ部屋を使っている。

My older sister and I share a room.

新しい計画について上司と相談しました。

I consulted with my supervisor about the new plan.

Structure: After a noun, と marks the other party in an interaction such as exchanging ideas or consulting.
Basic usage: In 同僚と意見を交換した。, the coworker is the person involved in the exchange.

Consulting together and seeking advice
- 上司と相談する highlights discussing something with a supervisor, while 上司に相談する highlights seeking advice from the supervisor. The same consultation can be presented from either perspective.
A reference for comparison
- The と in 姉と同じ部屋 marks the comparison counterpart for 同じ. Distinguish the relationship according to what follows, such as 交換する or 同じ.