reciprocal

Of a feeling, action or such: mutual, uniformly felt or done by each party towards the other or others; two-way.

reciprocal love

reciprocal duties

Mutually interchangeable.

These two rules will render a definition reciprocal with the thing defined.

Expressing mutual action, applied to pronouns and verbs; also in a broad sense: reflexive.

Used to denote different kinds of mutual relation; often with reference to the substitution of reciprocals for given quantities.

Done, given, felt, or owed in return.

a reciprocal invitation to lunch

The number obtained by dividing 1 by another given number; the result of exchanging the numerator and the denominator of a fraction.

0.5 is the reciprocal of 2.

A construction expressing mutual action.

Depending on where reciprocalization applies (syntax vs. lexicon), the relevant reciprocal verbs are claimed to exhibit specific properties, in particular: (i) syntactic reciprocals are fully productive whereas lexical reciprocals have only limited productivity; […]