νῦν now, at present often has a causal sense, as νῦν δέ but as the case stands, as it is; often to mark reality in contrast to an assumed case.
νῡνῑ́ (νῦν + deictic ῑ, 333 g) is stronger than νῦν: even now, at this moment; rarely in a causal sense.
νύ̆ν (enclitic; lyric, tragic, Herodotus, rare and suspected in Homer), a weakened form of νῦν, is rarely temporal, usually inferential, as now is used for then, therefore. νύν thus marks the connection of the speaker's thought with the situation in which he is placed. It is commonly used after imperatives, prohibitive and hortatory subjunctives. Thus, κάθιζε νύν με
seat me, then O. C. 21. In Xenophon and Plato νυν is written by some editors, where the Mss. have νῦν ( C. 4.2.37, H. 4. 1. 39).
νῡ́ν (enclitic) is adopted by some scholars in Attic tragedy where a long syllable is required ( O. T. 644). Others write νῦν (with the force of νύ̆ν).
νύ̆ (enclitic; Epic and Cyprian), a still weaker form of νῦν, and less emphatic than δή. It is common in questions and appeals; less frequent in statements; as τίς νυ; who now? Also after other particles, as καί νύ κε, ἦ ῥά νυ.