N-

Chemistry

 * n-, a lowercase prefix in chemistry denoting the straight-chain form of an open-chain compound in contrast to its branched isomer
 * N-, an uppercase prefix in chemistry denoting that the substituent is bonded to the nitrogen, as in amines

Mathematics, science and technology
The italicized letter n is used in mathematics to denote an arbitrary number (usually a non-negative integer).
 * n-ary associativity
 * n-ary code
 * n-ary group
 * n-back
 * n-body problem
 * n-category
 * n-category number
 * n-connected space
 * n-curve
 * n-dimensional space
 * n-dimensional sequential move puzzle
 * n-electron valence state perturbation theory (NEVPT)
 * n-entity
 * n-flake
 * n-gram
 * n-group
 * n-monoid
 * n-player game
 * n-skeleton
 * n-slit interferometer
 * n-slit interferometric equation
 * n-sphere
 * n-vector
 * n-vector model