Genitive Singular
Introduction
If the base ends in -α/, the genitive singular is marked by a lengthening of the -α to -η, as well as /ς. If the base ends in -ο/, the genitive singular is marked by /ο; the ο of the base contracts with the ο of the marker and becomes -ου. If the base ends in any other letter, the genitive singular is marked by /ος.
Intermediate
In the 1st declension, the feminine genitive singular marker is a lengthening of the -α to -η, as well as /ς:
κεφαλά/Lς > κεφαλῆς
Greek speakers treated /ου as the standard marker for the masculine genitive singular. So, for the rare masculine first declension nouns, the genitive singular is marked by this /ου:
ποιητά/ου > ποιητοῦ
In the 2nd declension, the genitive singular marker is /ο. The ο of the base contracts with the ο of the marker and becomes -ου:
ἄνθρωπο/ο > ἀνθρώπου
In the 3rd declension, the genitive singular marker is /ος.
λέοντ/ος > λέοντος
ἔρωτ/ος > ἔρωτος
ἄνακτ/ος > ἄνακτος
The consonants ϝ and σ drop when intervocalic. As a result:
βασιλέϝ/ος > βασιλέϝος > βασιλέος (Ionic)
ἀληθέσ/ος > ἀληθέσος > ἀληθέος (Ionic)
In Attic, after intervocalic ϝ drops from bases that end in –εσ/, -εος undergoes quantitative dissimilation to become -ηος, then quantitative metathesis to become -εως:
βασιλέϝ/ος > βασιλέος > βασιλῆος > βασιλέως (Attic)
In Attic, after intervocalic σ drops from bases that end in –εσ/, -εος contracts to -ους:
ἀληθέσ/ος > ἀληθέος > ἀληθοῦς (Attic)
Advanced
In the genitive singular and the genitive plural, the accent on monosyllabic bases falls on the final syllable of the final form:
νύκτ/ος > νυκτός
Vocabulary for this lesson (click here for the full lexicon)
reading morphologically 