The term 'A TIDE' is a combination of two words: 'A' and 'TIDE'. A TIDE is a natural phenomenon caused by the gravitational pull of the moon and sun on the Earth's oceans. The most common type of TIDE is the semi-diurnal TIDE, which has two high tides and two low tides each day. The other type of TIDE is the NEAP TIDE, which has only one high TIDE and one low TIDE each day. NEAP tides occur when the sun and moon are at right angles to each other, resulting in weaker tidal forces.