What is "spiritus lenis"

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).

n. (context orthography English) A diacritic mark in Ancient Greek used to indicate absence of aspiration for an initial vowel, and sometimes for a rho. (qualifier: ἀ, ῤ)