The following tables summarize the nominative and genitive endings for the three Greek noun declensions, with an example of each.
First declension
Nouns of the first declension have one important exception to the expected position of the accent: the genitive plural ending of the first declension is always accented with a circumflex. (There is a historical reason for this apparent exception, which has to do with the linguistic development of these forms over time: the circumflex reflects a vowel contraction similar to those you have seen in contract verbs.)
Masculine and feminine nouns of the first declension have different endings in the nominative and genitive singular. The vowel of feminine singular forms varies between eta and alpha, but note that the plural endings are the same for all first declension masculines and feminines.
Endings for feminine first-declension nouns that end in -η / -ης. Example: γνώμη, γνώμης, ἡ “judgment, opinion”
Case
Singular
Plural
Nominative
-η
-αι
Genitive
-ης
-ῶν
Case
Singular
Plural
Nominative
γνώμη
γνῶμαι
Genitive
γνώμης
γνωμῶν
Endings for feminine first-declension nouns that end in -ᾱ / -ᾱς. Example: θύρα, θύρας, ἡ “door”
Case
Singular
Plural
Nominative
-ᾱ
-αι
Genitive
-ᾱς
-ῶν
Case
Singular
Plural
Nominative
θύρα
θύραι
Genitive
θύρας
θυρῶν
Endings for feminine first-declension nouns that end in -ᾰ / ης. Example: θεράπαινα, θεραπαίνης, ἡ “female slave, servant”
Case
Singular
Plural
Nominative
-ᾰ
-αι
Genitive
-ης
-ῶν
Case
Singular
Plural
Nominative
θεράπαινα
θεράπαιναι
Genitive
θεραπαίνης
θεραπαινῶν
Endings for masculine first-declension nouns that end in -ης. Example: πολίτης, πολίτου, ὁ “citizen” (the iota is long).
Case
Singular
Plural
Nominative
-ης / -ᾱς
-αι
Genitive
-ου
-ῶν
Case
Singular
Plural
Nominative
πολίτης
πολῖται
Genitive
πολίτου
πολιτῶν
Second declension
Endings for masculine or feminine second-declension nouns that end in -ος / -ου. Example: ἄνθρωπος, ἀνθρώπου, ὁ or ἡ “person, human being”
Case
Singular
Plural
Nominative
-ος
-οι
Genitive
-ου
-ων
Case
Singular
Plural
Nominative
ἄνθρωπος
ἄνθρωποι
Genitive
ἀνθρώπου
ἀνθρώπων
Endings for neuter second-declension nouns that end in -ον / -ου. Example: παιδίον, παιδίου, τό “young child” or “young enslaved person”
Case
Singular
Plural
Nominative
-ον
-ᾰ
Genitive
-ου
-ων
Case
Singular
Plural
Nominative
παιδίον
παιδία
Genitive
παιδίου
παιδίων
Third declension
The third declension is sometimes called the “consonant declension” because most nouns in this declension have stems ending in a consonant. Because of linguistic changes to different kinds of stems, the basic endings summarized here appear in slightly different form in some patterns you will come to recognize over time. In particular, the relation between the nominative singular and genitive singular form may not appear obvious. Remember to use the genitive singular to find the stem for all other forms.
Note that the genitive singular ending in this declension, -ος, is the same as the masculine or feminine ending of the nominative singular form in the second declension. That reminds us that knowing what declension a noun belongs to, as well as what gender it is, is crucial for knowing what form the ending is indicating.
Take care as well with the neuter nominative plural ending in both the second and third declensions, -ᾰ, and one of the feminine nominative singular forms in the first declension, also -ᾰ.
Endings for masculine or feminine third-declension nouns. Example: μάρτυς, μάρτυρος, ὁ or ἡ, “witness”