Negative[x] gives True if x is a negative number.
NeighborhoodGraph[g, v] gives the graph neighborhood vertex v in the graph g. NeighborhoodGraph[g, {a_1, a_2, ...}] gives the graph neighborhood of the a_i that can be ...
NevilleThetaD[z, m] gives the Neville theta function \[CurlyTheta]_d (z \[VerticalSeparator] m).
NevilleThetaN[z, m] gives the Neville theta function \[CurlyTheta]_n (z \[VerticalSeparator] m).
NevilleThetaS[z, m] gives the Neville theta function \[CurlyTheta]_s (z \[VerticalSeparator] m).
NHoldAll is an attribute which specifies that none of the arguments to a function should be affected by N.
NHoldFirst is an attribute which specifies that the first argument to a function should not be affected by N.
NHoldRest is an attribute which specifies that all but the first argument to a function should not be affected by N.
NicholsGridLines is an option to NicholsPlot that specifies contours of constant magnitude and constant phase of the closed-loop system.
NIntegrate[f, {x, x_min, x_max}] gives a numerical approximation to the integral \[Integral]_x_min^x_max\ f\ d \ x. NIntegrate[f, {x, x_min, x_max}, {y, y_min, y_max}, ...] ...