Meaning of “twin” - Learner’s Dictionary

twin

noun [ C ] us uk /twɪn/
Extra Examples
People have difficulty distinguishing Tracy from her twin.It's impossible to tell the twins apart.When Jo told me she had a twin, everything fell into place.Michelle has had twins!There are three sets of twins in the school.

B1 one of two children who are born to the same mother at the same time

→ See also identical twin

(Definition of “twin noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)