Joint
Collaborative, Shared
の adjective, noun, verbal noun
If people work together on the same thing, they're working on a joint project. They're doing something collaborative.
共同 is used when two or more people or groups do something together with a shared purpose or responsibility. 共同作業 (collaborative work) means you share tasks with others, for example, and 共同生活 (shared living) means living together with someone, whether it's a partner or a roommate.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
チームメイトとの共同作業は楽しいです。
Collaborative tasks with teammates are fun.
ここは学生が共同で使うコーワーキングスペースです。
This is a co-working space for students to share.
彼は共同の貯金をこっそり使い果たしてしまった。
He secretly used up our joint savings.