[*] 27. Quantitative Vowel Gradation.—In the formation and inflection of words a short vowel often interchanges with its corresponding long vowel. Thus
| SHORT | α | ε | ι | ο | υ |
| LONG η (α_ after ε, ι, ρ, 31) | η | ι_ | ω | υ_ | |
| τι_μά-ω | ἐά-ω | φιλέ-ω | ἱκά_νω | δηλό-ω | φύ-σις |
| I honour | I permit | I love | I come | I show | nature |
| τι_μή-σω | ἐά_-σω | φιλή-σω | ἵ_κα_νον | δηλώ-σω | φῦ-μα |
| future | future | future | imperf. | future | growth |