Ocean currents are formed by a combination of factors, including wind, temperature, salinity, and the shape of the coastline.

1. Wind: The primary force driving ocean currents is wind. Surface winds create friction on the surface of the ocean, causing the water to move in the same direction as the wind. This is known as surface current. For example, the trade winds in the tropics blow from east to west, creating the Equatorial Currents.

2. Temperature and Salinity: Differences in temperature and salinity also contribute to the formation of ocean currents. Cold water is denser than warm water, so it sinks, while warm water rises. This creates a vertical movement of water known as upwelling and downwelling, which can influence the direction and strength of ocean currents. Salinity, or the amount of dissolved salt in the water, also affects density and can impact the movement of currents.

3. Shape of the Coastline: The shape of the coastline can influence the formation of ocean currents. When a current encounters a coastline, it is deflected by the shape of the land. This deflection is known as the Coriolis effect and causes currents to flow parallel to the coastline, creating coastal currents.

Related terms:
- Ocean Circulation: Ocean circulation refers to the global patterns of movement of ocean waters. It includes both surface currents, which are driven by wind, and deep currents, which are driven by density differences.
- Waves: Waves are the result of wind blowing across the surface of the ocean. They are created by the transfer of energy from the wind to the water, causing the water to move in a circular motion.
- Tides: Tides are the rise and fall of sea levels caused by the gravitational pull of the moon and the sun. Tides are influenced by ocean currents and can affect their direction and speed.