Neighbourliness is the habit of being friendly and helpful towards the people who live next to you — a wave, a borrowed tool, quiet at night, soup when someone is ill, help after a storm. English also stretches it to countries: neighbourliness between states means treating the country next door in a decent, helpful way, not picking fights. The word is a little old-fashioned and warm; it names a standing virtue more than one single act. British spelling keeps the u (neighbourliness); American spelling drops it (neighborliness). You will meet it in community talk, speeches, and writing about good manners between people who share a street — or a border.

睦鄰；鄰里情誼。國與國時也說睦鄰。