Related to, or caused by, the force of gravity — the pull between masses. A gravitational field is the space where that pull can be felt. The Moon’s gravitational pull helps make the tides. A gravitational wave is a tiny ripple in space from huge objects moving. It is the adjective that science prefers: we say gravitational force more often than gravity force. Though actually, everyday English still uses gravity in front of a noun sometimes (a gravity well, zero gravity), so you will meet both patterns. Gravitational just waves a clearer flag: ‘this is about that force’.