The Neuter Genitive

The neuters split by ending, and each shape has its own genitive pair. -ι nouns take -ιού / -ιών, moving the stress onto the ending: παιδί → παιδιού → παιδιών, σπίτι → σπιτιού → σπιτιών. -ο nouns behave exactly like the masculine -ος class, -ου / -ων, with the same shift where the word is long enough to need it: δώρο → δώρου → δώρων, νερό → νερού → νερών, φθινόπωρο → φθινοπώρου → φθινοπώρων. -μα nouns extend the stem to -ματ-: όνομα → ονόματος → ονομάτων, μάθημα → μαθήματος → μαθημάτων - and note that the tonos never stays on the first syllable, it travels right as the word grows. The usual neuter comfort holds throughout: nominative, accusative and vocative are identical, so in the singular the genitive is the only form you actually have to produce.