Spin-Spin Splitting Definition:

A phenomenon observed most commonly for nonequivalent protons connected to adjacent carbon atoms, in which the multiplicity of each signal is affected by the other.

Spin-Spin Splitting Explained:

This happens between the magnetic interactions of two nuclei observed in NMR- that are close to each other. Each particle has it’s own spin and momentum and in NMR-spectroscopy these properties allow the studied particles to be identified.