51 Ν before σ within a simple word disappears with lengthening of the vowel before it; ε becomes ει, o becomes oυ
([27 a](file:///x:/Departments/Classics_Texts/schoolgrammarofa00goodrich_porson/HTML%20Files/Chapter-027.html) and [28 b](file:///x:/Departments/Classics_Texts/schoolgrammarofa00goodrich_porson/HTML%20Files/Chapter-028.html)),-
- a. In some derivatives.
- b. In the accusative plural of ο stems (
[62 a](file:///x:/Departments/Classics_Texts/schoolgrammarofa00goodrich_porson/HTML%20Files/Chapter-062.html)).
- c. In the verb-ending -(ν)σι (older -ντι) (
[263 a](file:///x:/Departments/Classics_Texts/schoolgrammarofa00goodrich_porson/HTML%20Files/Chapter-263.html)).
- d. But in the dative plural ν before -σι disappears without vowel-lengthening.