What is the meaning of Nay?

No.

Introducing a statement, without direct negation.

Or rather, or should I say; moreover (introducing a stronger and more appropriate expression than the preceding one).

No.

A vote against.

A person who voted against.

A denial; a refusal.

To refuse.

Nary. (Can we add an example for this sense?)

swamp.

small river.

politics, political affairs, governance

Clipping of nanay.

that is today, or happening today

now, the present, as opposed to xưa (long ago; the past) and mai (later in the future)

Clipping of hôm nay (today)

Clipping of bữa nay (today)

Source: wiktionary.org