essentialpiece
nounUK /ɪˈsɛnʃəl piːs/
US /ɪˈsɛnʃəl pis/
A piece that you really need to make something work.
The wheel is an essentialpiece of the bicycle.
OTHER MEANINGS
2. The most important part of a plan or idea.
Trust is the essentialpiece of a good friendship.
3. A part that cannot be left out of a machine or tool.
The battery is an essentialpiece of the toy robot.
4. A person who is very important to a team or group.
Our coach called her the essentialpiece of the team.