neighborly vs neighbourly

neighborly and neighbourly both are adjectives.

Word	Noun	Adjective	Verb	Adverb
neighborly	No	Yes	No	No
neighbourly	No	Yes	No	No

As adjectives, neighborly and neighbourly are synonyms defined as:

neighborly and neighbourly: exhibiting the qualities expected in a friendly neighbor

neighborly (adjective)	neighbourly (adjective)
exhibiting the qualities expected in a friendly neighbor	exhibiting the qualities expected in a friendly neighbor