1. The process of converting an atom or molecule into an ion by adding or removing electrons.
Usage: British spelling; American English uses 'ionization'; Common in chemistry and physics contexts

Examples

• The ionisation of water molecules occurs when they are exposed to ultraviolet radiation.
• Ionisation chambers are used to detect radiation in nuclear physics experiments.
• The ionisation energy of an element determines how easily its electrons can be removed.
• Lightning causes rapid ionisation of air molecules in the atmosphere.
• Scientists study ionisation processes to understand plasma behavior.