|Origin:||compagnon, from Late Latin companio, from Latin com- ( COM-) + panis 'bread, food'|
com‧pan‧ion W3 [countable]
someone you spend a lot of time with, especially a friend:
For ten years he had been her constant companion.
His dog became his closest companion.
one of a pair of things that go together or can be used together
This book is a companion to Professor Farrer's first work.
companion volume/piece etc
The Encyclopedia of Gardening is a companion volume to the Encyclopedia of Plants and Flowers.
used in the titles of books about a particular subject:
A Companion to Japanese Literature
someone, especially a woman, who is paid to live or travel with an older person