The alternating rise and fall of the oceans of the world (usually twice a day) as they react to the gravitational attraction between the earth and the sun and the moon.
Tides are made up of two components, the height of the water and the flow of the current as the height changes. No two tides are the same height.
Some of the more common terms to describe various stages of tide are:
- Rising Tide - the vertical movement of water as the current flows in towards land.
- Falling Tide - the vertical movement of water as the current flows out from land.
- Current - the horizontal movement of water which leads to the rise and fall in the level of water.
- Flood Tide - the horizontal flow of water (current) towards the land. (This is the opposite of wind direction which is expressed in the direction the wind is blowing from).
- Ebb Tide - the horizontal flow of water (current) out to sea.
- Slack Water - the brief time when the current is not in motion as it reverses between flood and ebb and vice versa.
- High Tide or High Water - when the water reaches its greatest height in the tidal cycle.
- Low Tide or Low Water - when the water reaches its lowest height in the tidal cycle.
- Spring Tides - Tides which have the greatest range between low water and high water. This usually occurs once a month when the earth, sun, and moon are aligned and results in the greatest amount of current.
- Neap Tides - Tides which have the least range between low and high water. This usually occurs once a month when the earth, sun, and moon are out of alignment and results in the least amount of current.