c: an ecclesiastical anniversary or festival; also: its season —usually used in combination <Eastertide>
a (1): the alternate rising and falling of the surface of the ocean and of water bodies (as gulfs and bays) connected with the ocean that occurs usually twice a day and is the result of differing gravitational forces exerted at different parts of the earth by another body (as the moon or sun) (2): a less marked rising and falling of an inland body of water (3): a periodic movement in the earth's crust caused by the same forces that produce ocean tides(4): a periodic distortion on one celestial body caused by the gravitational attraction of another (5): one of the periodic movements of the atmosphere resembling those of the ocean and produced by gravitation or diurnal temperature changes
Middle English, from Old English tīdan; akin to Middle Dutch tiden to go, come, Old English tīd time
First Known Use: before 12th century
Medical Definition of TIDE
: a temporary increase or decrease in a specified substance or quality in the body or one of its systems <a postprandial alkaline tide, the typical rise in urinary pH associated with gastric acid secretion—E. J. Jacobson & Gerhard Fuchs>
Regular, periodic rise and fall of the surface of the sea, occurring in most places twice a day. Tides result from differences in the gravitational forces exerted at different points on the Earth's surface by another body (such as the Moon). Although any celestial body (e.g., Jupiter) produces minute tidal effects, the majority of the tidal forces on the Earth are raised by the Sun (because of its enormous mass) and the Moon (because of its proximity to Earth). In fact, the tidal forces from the Moon are about twice as strong as those from the Sun. The largest tides (spring tides, exhibiting very large change in sea level between high and low tides) occur at the new and full moon, when the Earth, the Moon, and the Sun are aligned and the Sun's tidal forces are added to those of the Moon. The smallest tides (neap tides) occur when the Sun and Moon are at right angles (from Earth), when the tidal forces from the Sun partially cancel those from the Moon. The geometry of the coastline and of the water's basin also affects the range of the tides.