one of two children or animals born at the same birth

experiments were carried out using sets of identical twins

the twins were approaching their third birthday

I thought you must have a double or be a twin

something containing or consisting of two matching or corresponding parts

forming, or being one of, a pair born at one birth

she gave birth to twin boys

her twin sister

link (a town or district) with another in a different country or cause (two towns or districts) to be linked, for the purposes of friendship and cultural exchange

the Russian city of Kostroma is twinned with Durham