The spiritus lenis ("soft breathing") or psilon pneuma (Greek: psilón, ψιλόν) 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). Allen¹ accordingly regards the glottal stop interpretation as "highly improbable".

The spiritus lenis is written as on top of or to the left of an initial vowel (the second vowel of a pair comprising a diphthong), and also in certain editions on the first of a pair of rhos. It did not occur on an initial upsilon. It takes the form of a closing half moon or a closing single quotation mark:

• ;

• Ἀ- Ἐ- Ἠ- Ἰ- Ὀ- Ὠ.

It is part of the traditional polytonic orthography for Greek, but has been dropped in the modern monotonic orthography as the [h] sound has disappeared from Modern Greek. The origin of the sign is thought to be the right-hand half–  ┤  –of the letter H, which was used in some Greek dialects as an [h] while in others it was used for the vowel eta.

Psila pneumata were also used in the early Cyrillic alphabet when writing the Old Church Slavonic language. In this context it is encoded as Unicode U+04806 or HTML entity ҆ ( ◌҆ ).

See also

• Spiritus asper
• Polytonic orthography

References

1. W. Sidney Allen, Vox Graeca - a guide to the pronunciation of classical Greek. Cambridge University Press, 1968-74. ISBN 0-521-20626-X