singular    nominative     ἡ    κόρ   η genitive    τῆς    κόρ   ης dative     τῇ   κόρ   ῃ accusative    τὴν   κόρ   ην vocative  ὦ   κόρ   η

plural nominative     αἱ   κόρ   αι genitive     τῶν   κορ   ῶν dative    ταῖς   κόρ   αις accusative    τὰς   κόρ   ας vocative    ὦ   κόρ   αι

 

Notes   The vocative is always the same as the nominative, in the singular as well as in the plural.   The genitive plural is always emphasized with a circumflex (sound drawn out, voice going up and then down again) on the last syllable. For all 1st declension nouns. But not adjectives! For adjectives the normal rules apply: emphasis on ultima (last syllable), circumflexed -ῶν, otherwise acute on penult (last but one) and unadorned final -ων.   Accentuation   All endings are long, except for nominative/vocative plural -αι, which, like the masculine plural -οι, is always short.   Which means that, if the penult carries the accent and is long, the acute will change to circumflex in the nominative/vocative plural. For example: ἡ κώμη, αἱ κῶμαι, the village, villages ἡ νίκη, αἱ νῖκαι, the victory, victories (just think of Nike sports-gear, meant to lead us to victory)   If the nominative form has an acute accent on the last syllable, that acute will change to circumflex in both genitive and dative (singular and plural). Take ἡ φωνή, τῆς φωνῆς, the voice (gramophone, phonetics, symphony, telephone...)

singular    nominative     ἡ    φων   ή genitive    τῆς    φων   ῆς dative  τῆ   φων   ῇ accusative    τὴν   φων   ήν

plural nominative     αἱ   φων   αί    genitive    τῶν   φων   ῶν dative    ταίς   φων   αῖς accusative    τὰς   φων   άς