i Register
In some senses, companion is marked as dated, obsolete. Watch for register when choosing this word.
ADJ
agreeable, amusing, boon, charming, delightful, good, entertaining, pleasant, wonderful | close, constant, faithful, inseparable | life | female, male | canine, human
dinner, drinking, travelling, walking
My sister is a great walking companion because she knows all the best trails in the countryside.
PREP
~ for/to
My older brother became a wonderful companion for me during those lonely years.