Definition - The contracting of two vowels into either one long vowel or a diphthong.

1. Usually, it involves combining a vowel that is at the end of a word with the one that starts the next word.
2. The term also denotes the internal contracting of Latin words (e.g. the creation of nil from nihil).

Etymology -
The word derives from the Greek krasis, mixture.

Oxford English Dictionary -
Its first citation is from 1833:
"Avoiding the hiatus…(1) by elision with the apostrophe; and (2) by contracting both syllables into one compound sound, or Crasis."
(E. Robinson tr. Buttmann's Larger Grk. Gram. 60)

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