Question

what is meant by 1-1 correspondence?

Answer 1

Two sets A and B have 1-1 correspondence
if
for each value of y in set B there is only one x in set A

Answer 2

it is one-to-one and onto.! :)

Answer 3

Every element of a set is paired with exactly one element of another.

Answer 4

@estudier is perfectly correct, by definition

Answer 5

To be absolutely clear, no elements remain unpaired.

Answer 6

Like :
(1,2), (3, 4), (7, 6)