Siamese twins (linguistics) Siamese twins (linguistics) Siamese twins (also irreversible binomials, binomials, binomial pairs, nonreversible word pairs, or freezes) in the context of the English language refer to a pair or group of words used together as an idiomatic expression or collocation, usually conjoined by the words "and" or "or". The order of elements cannot be reversed. The expressions "milk and honey" (two nouns), "short and sweet" (two adjectives), and "do or die" (two verbs) are various examples of Siamese twins. Many Siamese twins are "catchy" (and thus clichés and catchphrases) due to alliteration, rhyming, or their ubiquity in society and culture. Word
Monochorionic twins Monochorionic twins Monochorionic twins are monozygotic (identical) twins that share the same placenta. If the placenta is shared by more than two twins (see multiple birth), these are monochorionic multiples. Monochorionic twins occur in 0.3% of all pregnancies. 75% of monozygotic twin pregnancies are monochorionic; the remaining 25% are "dichorionic diamniotic". If the placenta divides, this takes place after the third day after fertilization. Monochorionic twins generally have two amniotic sacs (called Monochorionic-Diamniotic "MoDi"), but sometimes, in the case of monoamniotic twins (Monochorionic-Monoamniotic "MoMo"), they also share the same amniotic sac. Monoamniotic twins occur when the split takes place after