The spiritus lenis ("smooth breathing" or "soft breathing"), psilon pneuma (Greek: psilón, ψιλόν) or psilí, (Greek: ψιλή), is a
diacritical mark used in
Ancient Greek. It indicates the absence of initial aspiration: in other words, that the word does not begin with an [h] sound. Some authorities have interpreted it as representing a
glottal stop, but a final vowel at the end of a word is regularly elided where the following word starts with a vowel, which would not happen if the second word began with a glottal stop (or any form of stop consonant). Allen accordingly regards the glottal stop interpretation as "highly improbable".
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