From Longman Dictionary of Contemporary Englishtwintwin1 /twɪn/ ●●● S3 noun [countable] 
CHILDone of two children born at the same time to the same mother The twins are now eight months old. → identical twin, Siamese twin
CHILDone of two children born at the same time to the same mother The twins are now eight months old. → identical twin, Siamese twinExamples from the Corpus
twin• They look enough like each other to be twins.• Noelle and Craig are fraternal twins.• Sally and her twin sister still spend a lot of time together now that they are adults.• But for identical twins - who share the same genes - it rockets to 45 percent if one twin is already divorced.• There have been a lot of interesting studies done on identical twins separated at birth.• Identical twins, clearly, are far more concordant in general than are fraternal twins.• Evidence supporting a genetic component to predisposition comes mainly from a large study of 15924 male twin pairs.• Joey's my twin.• Split twins, passionate, dramatic, vicious, intelligent.• They take him, his brother Malachy, 3, and the twins, 1.• The twins stood over it, stirring the last embers with their feet.• I never realized that you and Sammy were twins.twintwin2 ●●○ adjective [only before noun] 1 used to describe one of two children who are twinstwin sister/brother Meet my twin sister.2 TIME/AT THE SAME TIMEused to describe two things that happen at the same time and are related to each other the twin problems of poverty and unemployment3 → twin room/bedroom → twinset, twin townExamples from the Corpus
twin• Some twin bedrooms which will have a balcony and sea view are available at a supplement.• I asked for a room with twin beds.• He was staring at the twin beds.• the new twin bridges over the river Clyde• It was Michael who introduced me to his twin brother Milton.• the twin cities of Minneapolis and St. Paul• a PC with twin disk drives• When I first saw them I thought they were twin girls.• The twin problems of ecological and individualist fallacies occur when inferences are drawn about one level of analysis using evidence from another.• twin towers• All bedrooms are twin with private bathroom; some with a balcony.twin sister/brother• She now believes the boy was her twin brother.• Sheer panic: Accused describes the barn fire that killed twin sisters.• I have a twin brother and it seemed that he was allowed to do all the things I wasn't.• My twin brother appeared by the age of about ten to have some hearing loss.• Some may find him placing far too much emphasis on the impact of his alcoholic parents and stillborn twin brother, Jesse.• Mr Goldring said that after Becky died her twin sister Katie was brought into the hospital purely for observation.• He has a twin brother named Arthur, who is also 126 at the university here.• These twin brothers were Giants, but they did not look like the monsters of old.twintwin3 verb (twinned, twinning) [transitive] 1 British English to form a relationship between two similar towns in different countries in order to encourage visits between thembe twinned with something Chichester in England is twinned with Chartres in France.2 PGto form a relationship between two places, people, or ideasbe twinned with something Dole has been twinned in the history books with his old rival Bush.Grammar Twin is usually passive. → twin town→ See Verb tableExamples from the Corpus
twin• None the less we are twinned with a small town in Hampshire with which we have no real connection.• The East Lothian town has been twinned with Champigny-sur-Marne for more than 30 years.Origin twin2 Old English twinn “double” 