Questions of Greek Grammar

...meaning it ends in ν nu with the vowel of the nominative:
ὁ μενέλεως Menelaus, τοῦ μενέλεω, τῷ μενέλεω, τὸν μενέλεων, ὦ μενέλεως; τὼ μενέλεω, τοῖν μενέλεων, ὦ μενέλεω; οἱ μενέλεω, τῶν μενέλεων, τοῖς μενέλεως, τοὺς μενέλεως, ὦ μενέλεω.

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ἡ ἅλως the threshing floor, τῆς ἅλω, τῇ ἅλῳ, τὴν ἅλων, ὦ ἅλως; τὰ ἅλω, ταῖν ἅλων, ὦ ἅλω; αἱ ἅλω, τῶν ἅλων, ταῖς ἅλως, τὰς ἅλως, ὦ ἅλω.

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τὸ εὔγεων the fertile land, τοῦ εὔγεω, τῷ εὔγεῳ, τὸ εὔγεων, ὦ εὔγεων; τὼ εὔγεω, τοῖν εὔγεων, ὦ εὔγεω; τὰ εὔγεω, τῶν εὔγεων, τοῖς εὔγεως, τὰ εὔγεω, ὦ εὔγεω.

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Fourth declension.

The fourth declension of the noun also exists in the three genders, and is isosyllabic, meaning all masculine and feminine nouns ending in ος omicron-sigma via the small ο omicron, and neuter nouns ending in ον omicron-nu, except for comparatives, whose genitive in all cases ends in ου omicron-upsilon; the dative ends in ῳ omega with iota subscript, and the accusative ends in ν with the vowel of the nominative.

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ὁ λόγος the word, τοῦ λόγου, τῷ λόγῳ, τὸν λόγον, ὦ λόγε, and ὦ λόγος; τὼ λόγω, τοῖν λόγοιν, ὦ λόγω; οἱ λόγοι, τῶν λόγων, τοῖς λόγοις, τοὺς λόγους, ὦ λόγοι.

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ἡ ὁδὸς the road, τῆς ὁδοῦ, τῇ ὁδῷ, τὴν ὁδόν, ὦ ὁδέ, and ὦ ὁδός; τὰ ὁδώ, ταῖν ὁδοῖν, ὦ ὁδώ; αἱ ὁδοί, τῶν ὁδῶν, ταῖς ὁδοῖς, τὰς ὁδούς, ὦ ὁδοί.

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τὸ ξύλον the wood, τοῦ ξύλου, τῷ ξύλῳ, τὸ ξύλον, ὦ ξύλον; τὼ ξύλω, τοῖν ξύλοιν, ὦ ξύλω; τὰ ξύλα, τῶν ξύλων, τοῖς ξύλοις, τὰ ξύλα, ὦ ξύλα.

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Fifth declension.