Sentence:  When in a <WSD>crasis</WSD>, a lene consonant ... is combined with an aspirated vowel, the lene is always changed (except in the Ionic dialect) into the corresponding aspirate ... 
Meaning of the word marked with <WSD> tags:  External vowel sandhi; contraction of a vowel or diphthong at the end of a word with a vowel or diphthong at the start of the following word.