1twin 
/ˈtwɪn/ noun
plural twins /ˈtwɪn/ noun [count] 1 : either one of two babies that are born at the same time to the same mother
▪ She's the mother of twins. ▪ The twins went swimming after lunch. ▪ My sister just had twins. ▪ Sarah and her brother are twins. ▪ I didn't know she had a twin. [=a sister/brother who is her twin] — compare quadruplet, quintuplet, sextuplet, triplet; see also conjoined twin, fraternal twin, identical twin 2 : either one of two similar things that form a pair
▪ I found one glove but I can't find its twin. [=I can't find the other glove]
▪ She's the mother of twins. ▪ The twins went swimming after lunch. ▪ My sister just had twins. ▪ Sarah and her brother are twins. ▪ I didn't know she had a twin. [=a sister/brother who is her twin] — compare quadruplet, quintuplet, sextuplet, triplet; see also conjoined twin, fraternal twin, identical twin
▪ I found one glove but I can't find its twin. [=I can't find the other glove]
