What is "smooth breathing"

Breathing \Breath"ing\, n.

1. Respiration; the act of inhaling and exhaling air.

   Subject to a difficulty of breathing.
   --Melmoth.

2. Air in gentle motion.

3. Any gentle influence or operation; inspiration; as, the breathings of the Spirit.

4. Aspiration; secret prayer. ``Earnest desires and breathings after that blessed state.''
   --Tillotson.

5. Exercising; promotion of respiration.

   Here is a lady that wants breathing too; And I have heard, you knights of Tyre Are excellent in making ladies trip.
   --Shak.

6. Utterance; communication or publicity by words.

   I am sorry to give breathing to my purpose.
   --Shak.

7. Breathing place; vent.
   --Dryden.

8. Stop; pause; delay.

   You shake the head at so long a breathing.
   --Shak.

9. Also, in a wider sense, the sound caused by the friction of the outgoing breath in the throat, mouth, etc., when the glottis is wide open; aspiration; the sound expressed by the letter h.

10. (Gr. Gram.) A mark to indicate aspiration or its absence. See Rough breathing, Smooth breathing, below. Breathing place.

    1. A pause. ``That c[ae]sura, or breathing place, in the midst of the verse.''
       --Sir P. Sidney.

    2. A vent.

       Breathing time, pause; relaxation.
       --Bp. Hall.

       Breathing while, time sufficient for drawing breath; a short time.
       --Shak.

       Rough breathing ( spiritus asper) ([spasp]). See 2d Asper, n.

       Smooth breathing ( spiritus lenis), a mark (') indicating the absence of the sound of h, as in 'ie`nai (ienai).

The smooth breathing (; psilí; ) is a diacritical mark used in polytonic orthography. In ancient Greek, it marks the absence of the voiceless glottal fricative from the beginning of a word.

Some authorities have interpreted it as representing a glottal stop, but a final vowel at the end of a word is regularly elided (removed) when the following word starts with a vowel and elision would not happen if the second word began with a glottal stop (or any other form of stop consonant). In his Vox Graeca, W. Sidney Allen accordingly regards the glottal stop interpretation as "highly improbable".

The smooth breathing ( ) is written as on top of one initial vowel, on top of the second vowel of a diphthong or to the left of a capital and also, in certain editions, on the first of a pair of rhos. It did not occur on an initial upsilon, which always has rough breathing (thus the early name hy, rather than y).

The smooth breathing was kept in the traditional polytonic orthography even after the sound had disappeared from the language in Hellenistic times. It has been dropped in the modern monotonic orthography.