Spiritus asper

The spiritus asper ("rough breathing") is the mark of an initial aspiration in ancient Greek. It is written as an opening half moon on top of or to the left of an initial vowel and rho:

• ἁ- ἑ- ἡ- ἱ- ὁ- ὑ- ὡ- ῥ-;
• Ἁ- Ἑ- Ἡ- Ἱ- Ὁ- Ὑ- Ὡ- Ῥ-.

The only situations when it can be written inside a word is :

• on top of a double rho in certain editions;
• when it represents a coronis resulting from a grapheme which is a vowel not preceded by an [h], the spiritus lenis ("soft breath") must be employed.