General words:
* Communal: Relating to or shared by a community.
* Communicate: To share information or ideas.
* Communion: A shared feeling or experience.
* Community: A group of people living in the same place or sharing a common interest.
* Commute: To travel regularly between home and work.
* Common: Belonging to or shared by all members of a group.
More specific words:
* Communist: A person who believes in communism.
* Communism: A political theory advocating class war and leading to a society in which all property is publicly owned.
* Communique: An official announcement or statement.
* Communicate: To convey information or ideas.
* Commemorate: To mark an event by a ceremony or activity.
* Conviviality: A lively and enjoyable atmosphere, especially created by people being together.
Less common words:
* Communicable: Able to be spread from person to person.
* Communicate: To share or transmit information or feelings.
* Communicate: To make common; to share.
* Commute: To exchange one thing for another.
* Communicate: To connect or unite.
* Commemorate: To keep the memory of (someone or something) alive.
This is not an exhaustive list, but it gives you a good starting point. You can find more words by searching online dictionaries or etymology websites.