After some preliminary remarks about Plato’s use of the adverb nun, I explain what the nun is by offering a close textual analysis of the key passage in which it is explicitly addressed (Parm. 151e3–153b7). Its metaxu nature, between duration and limit, requires one to consider another temporal notion of the second part of the Parmenides that is metaxu, namely the exaiphnês. I explain why the nun does not conceptually overlap with the exaiphnês, arguing moreover that there is no model where both notions fit, but rather a model accounting for a switch and another one accounting for continuous change.