- Equinumerosity
In the field of

mathematics , two sets "A" and "B" are**equinumerous**if they have the samecardinality , i.e., if there exists abijection "f" : "A" → "B". This is usually denoted:$A\; approx\; B\; ,$ or $A\; sim\; B$.

The study of cardinality is often called

**equinumerosity**("equalness-of-number"). The terms**equipollence**("equalness-of-strength") and**equipotence**("equalness-of-power") are sometimes used instead.In

**Set**, the category of all sets with functions as morphisms, anisomorphism between two sets is precisely a bijection, and two sets are equinumerous precisely if they are isomorphic in this category.**ee also***

Category of sets

*Cardinal number

*Cardinality

*Bijection

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