Fortune and retribution
The word nemesis originally meant the distributor of fortune, neither good nor bad, simply in due proportion to each according to what was deserved. Later, Nemesis, in Herodotus and Pindar it came to suggest the resentment caused by any disturbance of this right proportion, the sense of justice that could not allow it to pass unpunished.
O. Gruppe (1906) and others connect the name with "to feel just resentment". From the fourth century onward, Nemesis, as the just balancer of Fortune's chance, could be associated with Tyche.
Divine retribution is a major theme in the Greek world view, providing the unifying theme of the tragedies of Sophocles and many other literary works. Hesiod states: "Also deadly Nyx bore Nemesis an affliction to mortals subject to death" (Theogony, 223, though perhaps an interpolated line). Nemesis appears in a still more concrete form in a fragment of the epic Cypria.
She is implacable justice: that of Zeus in the Olympian scheme of things, although it is clear she existed prior to him, as her images look similar to several other goddesses, such as Cybele, Rhea, Demeter, and Artemis.
In the Greek tragedies Nemesis appears chiefly as the avenger of crime and the punisher of hubris, and as such is akin to Atë and the Erinyes. She was sometimes called Adrasteia, probably meaning "one from whom there is no escape"; her epithet Erinys ("implacable") is specially applied to Demeter and the Phrygian mother goddess, Cybele.