mutuality

1. Having the same relationship each to the other: mutual predators.

2. Directed and received by each toward the other; reciprocal: mutual respect.

3. Possessed in common: mutual interests.

4. Of, relating to, or in the form of mutual insurance.

Usage Note: Mutual is used to describe a reciprocal relationship between two or more people or things. Thus their mutual animosity means "their animosity for each other" or "the animosity between them," and a mutual defense treaty is one in which each party agrees to come to the defense of the other. But many people also use mutual to mean "shared in common," as in The bill serves the mutual interests of management and labor. This usage is perhaps most familiar in the expression our mutual friend, which was widespread even before Charles Dickens used it as the title of a novel. While some language critics have objected to this usage because it does not include the notion of reciprocity, it appears in the writing of some of our greatest authors, including Shakespeare, Edmund Burke, George Eliot, and James Joyce, and it continues to be used by well-respected writers today.