共同 and 共有: joint activity and the scope of sharing
Compare joint garden management and material development in 共同 with meeting materials and family photos in 共有. Identify the activity, shared object, and participants without assuming completion or public access.
共同: managing a garden and developing a material
共同 (きょうどう) describes activity carried out jointly. 「近所の人と共同で小さな菜園を管理する。」 means “I maintain a small vegetable garden jointly with a neighbor.” 近所の人と identifies the person involved, and 共同で says that the management is done together.
「両社は新しい素材を共同開発している。」 means “The two companies are jointly developing a new material.” The two companies are the participants, and the new material is what they are developing. 開発している describes ongoing development, rather than a material that has already been completed or released.
共有: meeting materials and a family-only photo album
共有 (きょうゆう) focuses on sharing something. 「会議の前に資料を全員と共有した。」 means “I shared the materials with everyone before the meeting.” The materials are the shared object, and 全員と identifies the people involved. “Everyone” here should not be expanded to every unrelated person.
「旅の写真を家族だけのアルバムで共有している。」 means “We share travel photos in a family-only album.” 旅の写真 identifies what is shared, while 家族だけ limits the album to family. Sharing the photos does not mean that anyone can view them publicly.
Find the joint activity or the shared object
For 共同, ask what the participants do together: a neighbor joins in managing a garden, and two companies develop a material. For 共有, ask what is shared and with whom: materials are shared with everyone in the meeting context, while travel photos are shared in a family-only album.
Joint management or development does not establish equal ownership shares. Sharing materials or photos likewise does not, by itself, specify legal rights or detailed access permissions. Keep the activity and participants stated in the sentence, including the family-only limit and the ongoing state of development.
Are the travel photos shared in a family-only album publicly available to anyone?
Show the answer and why
No. They are shared in a family-only album, so the family-only scope must be preserved. 共有 does not turn that limited sharing into public access.