1. The result arising from the differential gravitational effect of one body on another: Tides on Earth can be sea tides or small land tides.

A tide usually manifests itself in the distortion of the shape of the body, especially the surface layers.

2. Periodic changes in the shape of a planet, moon, or star caused by the gravitational attraction of a body near it: The Moon tugs on Earth's oceans, causing high and low tides; while Jupiter's gravitational attraction on its moon causes ground tides, and when two stars are very close together, they pull each other's atmospheres into distorted shapes.

A tide of decreased range that occurs twice a month: A neap tide takes place when the Moon is in quadrature, that is during its first and last quarters, when the Sun and the Moon are at right angles to each other relative to the Earth.

The neap tide takes place on the Earth when the Sun and Moon are in positions forming a right angle at the Earth's center.

The Sun and Moon largely cancel each other out, resulting in an extra low high tide and an extra high low tide.

The tide on the Earth's surface when the effect of the Moon and Sun is greatest: Spring tide occurs at new and full moon and when the Moon and Sun are in line.