A Short Grammar of Classical Greek: Part II: Inflection I: Inflection of Nouns and Adjectives.

1. In the endings -ως and -ων, ω is accounted short.

2. All words in -ις, -εως are barytone. Most of them are feminines in -σις and denote action, as ἡ λύσις the loosing, ransoming, release; ἡ πρᾶξις the doing, deed.

1. In nouns in -υς, the stem characteristic -υ remains throughout (cf. 2); the acc. plur. ends in -ῡς (for -υνς).

2. Τὸ ἄστυ the city (esp. of Athens) is inflected like ι-stems:
τὸ ἄστυ, ἄστεως, ἄστει, ἄστυ,
τὰ ἄστη, ἄστεων, ἄστεσι(ν), ἄστη.

3. Adjectives have two stems in the masc. and neut.: ἡδυ- in the nom., acc., voc. sing.; everywhere else ἡδε- (for ἡδεϝ-).

1. All words in -ευς are masculine oxytones. Note the quantity of the endings -ως, -ᾰ and -ᾱς.

2. In old Attic the nom. plur. ends in -ῆς: οἱ βασιλῆς. In poetry, and occasionally in prose, the acc. plur. ends in -εῖς: τοὺς γονεῖς.

3. Words in -εύς with a preceding vowel are often contracted in the gen. and acc. sing. and plur., and thus
-έω becomes -ῶ: τοῦ Πειραιῶς, τῶν Εὐβοιῶν,
-έα becomes -ᾶ: τὸν Πειραιᾶ, τοὺς Ἐρετριᾶς.

4. Ὁ ἡ βοῦς (bos, bovis) ox, cow retains the stem βου- only when the ending is, or begins with, a consonant: βοῦς, βοῦν, βουσί(ν); but otherwise changes it to βο-, without admitting contraction; hence
ὁ ἡ βοῦς, βοός, βοΐ, βοῦν,
βόες, βοῶν, βουσί(ν), βοῦς.

1. The few stems in -ω do not admit of contraction.
2. Words with stems in -ο are feminine oxytones, and mostly proper names; they are found in the singular only.

Irregularities in the declension of nouns arise chiefly from the fact that the cases of a word are formed from two different stems. The following are the most common irregular nouns:

1. ἡ γυνή woman derives all its other forms from the stem γυναικ-. The accentuation is that of monosyllabic consonant stems (36, 6):
ἡ γυνή, γυναικός, γυναικί, γυναῖκα, γύναι,
γυναῖκες, γυναικῶν, γυναιξί(ν), γυναῖκας, γυναῖκες.

2. Ζεύς the god Zeus (stems Ζευ- and Δι-):
Ζεύς, Διός, Διΐ, Δία, Ζεῦ.

3. ὁ ἡ κύων dog (stems κυον- and κῠν-):
ὁ ἡ κύων, κυνός, κυνί, κύνα, κύον,
κύνες, κυνῶν, κυσί(ν), κύνας, κύνες.

4. ὁ μάρτυς witness (stems μαρτῠ- and μαρτῠρ-):
ὁ μάρτυς, μάρτυρος, μάρτυρι, μάρτυρα,
μάρτυρες, μαρτύρων, μάρτυσι(ν), μάρτυρας.

5. ἡ ναῦς ship (stem ναυ-, νᾱϝ-, νᾱυ-is, νηϝ-):
ἡ ναῦς, νεώς, νηΐ, ναῦν,
νῆες, νεῶν, ναυσί(ν), ναῦς.

6. τὸ ὄναρ dream (stems ὀναρ- and ὀνειρατ-):
τὸ ὄναρ, ὀνείρατος, ὀνείρατι, ὄναρ,
τὰ ὀνείρατα, ὀνειράτων, ὀνείρασι(ν), ὀνείρατα.
Also ὁ ὄνειρος and τὸ ὄνειρον are found.

7. ὁ πρεσβευτής ambassador borrows the plural from πρέσβυς old, venerable. Hence
ὁ πρεσβευτής, -τοῦ, -τῇ, -τήν, -τά,
οἱ πρέσβεις, πρέσβεων, πρέσβεσι(ν), πρέσβεις.

8. τὸ πῦρ fire is inflected in the singular according to the consonantal, in the plural according to the O-declension:
τὸ πῦρ, πυρ-ός, πυρ-ί,
τὰ πυρ-ά, πυρ-ῶν, πυρ-οῖς, watchfires.

9. ὁ σῖτος corn, food is neuter in the plural:
τὰ σῖτα, σίτων, σίτοις.

10. τὸ στάδιον stadium (a measure of length) has in the plur. both οἱ στάδιοι and τὰ στάδια.

11. ὁ υἱός son (besides the regular forms according to the O-declension) forms some cases from the stem υἱε- (compare ἡδύς)
in the sing. υἱέ-ος, υἱεῖ,
in the plur. υἱεῖς, υἱέ-ων, υἱέ-σι(ν), υἱεῖς.

12. ἡ χείρ hand is regular, except in the dat. plur.: χερ-σί(ν)

These are mostly applied to the stem:
-θεν denoting: whence,
-ι and -θι in the sing., denoting: where,
-σι(ν) in the plural,
-δε, -σε, -ζε denoting: whither.

E.g. οἴκοθεν from home, οἴκοι at home, οἴκαδε home(ward),
ἄλλοθεν aliunde, ἄλλοθι alibi, ἄλλοσε alio,
Ἀθήνηθεν from Athens, Ἀθήνησι(ν) at Athens, Ἀθήναζε to Athens,
πάντοθεν from all sides, Μαραθῶνι at Marathon, Μέγαράδε to Megara (9, 1. f.),
χαμᾶθεν from the ground, χαμαί humi, χαμάζε to or on the ground.

Note. — The forms in -ι are relics of an original locative sing., those in -σι(ν), of a locative plur.

The masculine and the neuter of these adjectives are formed from the same stem. The feminine always follows the A‑Declension.

1. Stems in -ο. Decl. 32.
ἀγαθός, ἀγαθή, ἀγαθόν good,
δίκαιος, δικαία, δίκαιον just.

2. Contracted adjectives with stems in -ο. Decl. 34.
ἀργυροῦς, ἀργυρᾶ, ἀργυροῦν silver,
χρυσοῦς, χρυσῆ, χρυσοῦν golden,
ἁπλοῦς, ἁπλῆ, ἁπλοῦν simple.

3. Stems in -υ. Decl. 40.
μέλᾱς, μέλαινα, μέλαν black,
τάλᾱς, τάλαινα, τάλαν (poet.) wretched.

4. Stems in -ντ. Decl. 41.
πᾶς, πᾶσα, πᾶν whole, all,
ἄκων, ἄκουσα, ἆκον unwilling,
ἑκών, ἑκοῦσα, ἑκόν willing,
λυθείς, λυθεῖσα, λυθέν loosed.

5. Stems in -υ (almost all oxytone). Decl. 47.
ἡδύς, ἡδεῖα, ἡδύ sweet,
ἥμισυς, ἡμίσεια, ἥμισυ half.

The stem is the same for all genders; the masculine and feminine are alike in form.

1. Stems in ‑ο (especially compound adjectives). 32, 3 seqq.

βάρβαρος, ‑ον foreign, ἄτιμος, ‑ον dishonored,
ἥσυχος, ‑ον quiet, ἔντιμος, ‑ον honored,
φρόνιμος, ‑ον prudent, παράνομος, ‑ον unlawful,
πρᾶος, ‑ον mild, tame, πανοῦργος, ‑ον cunning.

Note. — Adjectives of two and three endings are mentioned in 32, 4: βέβαιος, 2 and 3, firm, stable; ὠφέλιμος, 2 and 3, profitable.

2. Contract adjectives with stems in ‑ο. Decl. 33.

εὔνους, εὔνουν well-disposed,
σύμπλους, σύμπλουν sailing with.

3. Stems in ‑ω (according to the Attic decl.). Decl. 35.

ἵλεως, ἵλεων propitious,
ἔκπλεως, ἔκπλεων full.

4. Stems in dental mutes (esp. compounds of nouns). 39.

ἄχαρις, ‑ι unpleasant (ἀχάριτος, ἀχάριτι, ἄχαριν, ‑ι),
εὔελπις, ‑ι hopeful (εὐέλπιδος, εὐέλπιδι, εὔελπιν, ‑ι),
ἄπολις, ‑ι homeless (ἀπόλιδος, ἀπόλιδι, ἄπολιν, ‑ι).

5. Stems in ‑ν. Decl. 40.

εὐδαίμων, εὔδαιμον happy,
σώφρων, σῶφρον prudent,
κακίων, κάκιον worse,
ἄρρην, ἄρρεν male.

6. Stems in ‑εσ. Decl. 45.

εὐγενής, ‑ές of noble race,
συνήθης, σύνηθες customary,
ἐνδεής, ‑ές needy,
ὑγιής, ‑ές healthy.

A few adjectives have but one termination for all three genders. On account of their meaning, however, they are rarely used in the neuter. They have nearly all a dental stem.

φυγάς, φυγάδος fugitive, exiled,
πένης, πένητος needy, poor,
μάκαρ, μάκαρος blessed, happy.

Note. — Masculine only is the adjective ἐθελοντής, ‑οῦ voluntary, volunteer. Feminine only are the adjectives in ‑ίς, ‑ίδος, as συμμαχίς, ‑ίδος allied, Ἑλληνίς, ‑ίδος a Grecian woman, ἡ πατρίς (sc. γῆ) one’s native country.

The two adjectives μέγας, μεγάλη, μέγα great, tall and πολύς, πολλή, πολύ much, pl. many derive all their forms, except the nom. and acc. sing. masc. and neut., from the stems μεγαλο‑ and πολλο‑ respectively.