The old dog had been her 'constant companion' for over 12 years. [=had been with her most of the time for 12 years]
The book is a 'companion to' the television series with the same name.
The book is the 'companion' volume 'to' his previous book on jazz.
(..) to put the-- It's okay. It's okay. I'll keep your secret if you keep mine. A congressman, you say? Right now, I'm just a drinking companion. Well, all right, companion. Have yourself a drink. Come on in. $. What will that get me? (..)2013 TvShow: House of Cards Title: Chapter 2 Season: 1 Episode 2