As we have seen in the different declination kein can be used with or without a noun, that means that it can be used as adjectival (with noun) and as substantival (without noun) pronoun. The word kein changes marginally in masculine and neutral form.

Examples:

Kein Mann sieht Fußball. = No man watches soccer. Keiner sieht Fußball. = No one / nobody watches soccer. Ich sehe keinen Mann. = I do not see a man. Ich sehe keinen. = I do not see anyone / anybody. (thinking still of a masculine noun) Ich schenke es keinem Mann. = I do not give it to a man. Ich schenke es keinem. = I do not give it anyone / anybody.

Actually it works the same with feminine nouns:

Examples:

Keine Frau sieht rote Elefanten. = No woman sees red elephants. Keine sieht rote Elefanten. = No one / nobody sees red elephant (no feminine person) Ich sehe keine Frau. = I do not see a woman. Ich sehe keine. = I do not see anyone / anybody. (thinking still of a feminine noun) Ich schenke es keiner Frau. = I do not give it to a woman. Ich schenke es keiner. = I do not give it anyone / anybody. (still having the feminine in mind)

and as well with neutral ones.

Examples:

Kein Kind kauf rote Elefanten. = No child buys red elephants. Keines kauft rote Elefanten. = No one / Nobody buys red elephants. Er sieht kein Kind. = He does not see a child. Er sieht keines. = He does not see anyone / anybody. (thinking still of a neutral noun) Er schenkt es keinem child. = He does not give it to a child.. Er schenkt es keinem. = He does not give it anyone / anybody. (still having the neutral in mind)