Two sets that contain the same number of elements are called equinumerous sets.
The term ‘equinumerous’ comes from the combination of ‘equi’ meaning equal, and ‘numerous’ which refers to the number of elements. In simpler terms, if you can find a one-to-one correspondence between the elements of the two sets, they are equinumerous. This concept is fundamental in set theory, as it helps us understand the sizes of sets, especially when they are infinite.