https://doi.org/10.1351/goldbook.Q05003
Derivatives of @[email protected], (NH4+)Y−, in which all four of the hydrogens bonded to nitrogen have been replaced with @[email protected] groups. Compounds having a carbon-nitrogen double bond (i.e. R2C=N+R2Y−) are more accurately called @[email protected] e.g. [(CH3)4N]+OH−, tetramethylammonium hydroxide.
See:
onium compounds