(CW) A continuous wave is an electromagnetic wave of constant amplitude and frequency (emitting continuously, not pulsed). Continuous wave lasers are used in spectroscopy.

(CW) A technique for studying NMR by continuously applying RF radiation to the sample and slowly sweeping either the RF frequency or the magnetic field through the resonance values; now largely superceded by pulse MR technique.

(AFP) Adiabatic fast passage is a NMR technique of producing rotation of the macroscopic magnetization vector by shifting the frequency of RF energy pulses (or the strength of the magnetic field) through resonance (the Larmor frequency) in a time short compared to the relaxation times. Particularly used for inversion of the spins between high and low energy states with an excess of spins in the higher energy level. A continuous wave NMR technique used in e.g., MR spectroscopy.

A technique that uses RF pulses and Fourier transformation of the MR signal; have largely replaced the older continuous wave techniques.

For the wide uses of NMR spectroscopy (from mineralogy to medicine) there is a variety of different spectroscopic imaging techniques available.
A short listing of the most frequent variations: