1.ConjunctionUsed when negating two or more elements, and not, not A or B, not A nor B, neither A nor B
"No es (ni) A ni B.; No es (ni) A, ni B ni C.; Ni A ni B es. [The first ni is mandatory here because the verb es isn't before it. Es can't be preceded by no in this example for the same reason.]; Ni es A ni (es) B. [The first ni is mandatory because there isn't a verb es before it.]"
2.AdverbUsed in emphatic negations, not even
"No tengo ni tiempo.; Ni tiempo tengo. [Like in the example in the conjunction sense, the verb isn't negated.]; Ni tengo tiempo.; Ni yo tengo ni tiempo."
3.AdverbForms an emphatic negative imperative, don't even