A greeting is a tiny agreement to acknowledge another person’s existence.

A greeting conveys almost no information and does something else entirely. It confirms that you have registered another person as present and worth acknowledging, which is a small transaction that most social warmth is built on. Withholding it is felt immediately, even by people who could not say why.

Greet the people you routinely pass without greeting, the person at the desk, the neighbour, the driver. It costs a second. The cumulative effect on how a place feels, including for you, is out of all proportion to the effort involved.