twin

noun

• 1one 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
• a person or thing that is exactly like another:there was a bruise on his cheek, a twin to the one on mine
• (the Twins) the zodiacal sign or constellation Gemini.

• 2something containing or consisting of two matching or corresponding parts, in particular:
• a twin-bedded room: the hotel has 54 rooms, of which 4 are twins
• a twin-engined aircraft.
• a twinned crystal.

adjective

• forming, or being one of, a pair born at one birth:she gave birth to twin boys her twin sister
• forming a matching, complementary, or closely connected pair:the twin problems of economic failure and social disintegration
• Botany growing in pairs:twin seed leaves
• (of a bedroom) containing two single beds: we have twin and three-bedded rooms
• (of a crystal) twinned.

verb (twins, twinning, twinned)

• 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
• link; combine:the company twinned its core business of brewing with that of distilling