Nun is the primordial water - the inert, formless abyss that existed before creation and out of which the benben mound and Atum rose. In the Hermopolitan Ogdoad he is the male of the pair Nun and Naunet, and from the Middle Kingdom he is 'the father of the gods'; the solar barque sails on him in the underworld. He is the substance of beginning rather than a god with a myth of his own.
Modern Practice
Nun is worked with at the start of a thing and at its dissolution: a bare bowl of water, silence, and no request. The practice is to let the formlessness be there rather than to fill it.
Nun = 50, ordinal 14, reduced 5, final form ן = 700. Spelled in full, נון = 50+6+50 = 106.
Meaning
Nun is 'fish', one of the twelve simples, and the letter of the one who comes out of the water — Joshua son of Nun — as well as of the fish that swims in the Torah's sea. Its 50 is the number of the Jubilee and of the gates of understanding, the point beyond the seven weeks at which the count begins again.