mutual; reciprocal
Mutual respect
Reciprocal protection in wartime
Your mutual animosity comes to nothing; your mutual animosity is of no avail
mutually; each other; one another
As a general rule, mutually opposed tendencies result in war
His three sisters are always envious of one another; his three sisters always envy one another
The two girls imitate each other by wearing identical hats
To reciprocate each other's greetings; to exchange greetings (with each other)