1. The process of granting citizenship to a foreign-born person who meets legal requirements.
Usage: British English spelling; American English uses 'naturalization'; Legal/administrative context
2. The process of adapting or becoming accustomed to a new environment or culture.
Usage: General/figurative use
3. The introduction and establishment of a plant or animal species in a region where it is not native.
Usage: Biology/ecology context

Examples

• She completed her naturalisation process and became a citizen after five years of residency.
• The immigrant's naturalisation into the community took time but was ultimately successful.
• The rabbit species underwent naturalisation in the new habitat over several generations.
• Naturalisation ceremonies are held regularly to welcome new citizens.
• The plant's naturalisation in the region surprised ecologists who expected it to fail.
• His naturalisation as a member of the club happened gradually through regular participation.