The neuter word ἔργον on p35 of Duff follows the other pattern grouped with λόγος in the second declension. If you study the pattern you can see why – the genitive and dative endings are exactly the same as λόγος. The change in pattern is in the nominative and accusative forms, so this is the only difference that needs to be learnt.

This pattern, by the way, is why it is correct to say one criterion, and many criteria – criterion has come into English from Greek, and its cri-root means judge or judgement (as in crisis, critical, etc).

So: neuter second declension words ending in – ον will follow this pattern. You get to the stem by removing the – ον, then add the endings as for ἔργον .

singularplural
nominativeἔργονἔργα
accusativeἔργονἔργα
genitive ἔργουἔργων
dativeἔργῳἔργοις
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There is a neuter form for the definite article that must be used with neuter nouns (see p36 of Duff).

singularplural
nominativeτότά
accusativeτότά
genitiveτοῦτῶν
dativeτῷτοῖς
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Notice that the only differences from the form o f ‘the’ used in front of masculine nouns are in the nominative and accusative forms. As for all neuter nouns, the nominative and accusative forms are the same.