Perispomeni

Rules for using the Perispomeni (Circumflex)

Source: wiktionary

Graphically these symbols are somewhat different from their counterparts used with the Latin letters—the acute and grave accents are generally drawn with a much steeper angle than is used with Latin letters, and the perispomeni appears, depending on font design, as a circumflex, tilde, or inverted breve.

Source: wiktionary

The remaining three diacritics, oxia ( ΄ ), varia ( ` ), and perispomeni ( ˜ ), are used in the text to indicate primary stress.

Source: wiktionary