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satellite image of the
Nile River delta, Egypt
1. The fourth letter of the Greek alphabet. See Table at alphabet.
2. An object shaped like a triangle.
a. A usually triangular alluvial deposit at the mouth of a river.
b. A similar deposit at the mouth of a tidal inlet, caused by tidal currents.
4. Mathematics A finite increment in a variable.
1. Being in the fourth position relative to a designated carbon atom in an organic molecule at which an atom or a group may be substituted.
2. Referring to the fourth of a group of isomers, or molecules of similar origin or properties, determined arbitrarily by those who discover or classify them. Used in combination.
del·ta′ic (-tā′ĭk), del′tic (-tĭk) adj.
An area of the south-central United States extending on either side of the Mississippi River from Memphis, Tennessee, to Vicksburg, Mississippi. An important cotton-producing region, it is noted for its folk culture, especially as the home of some of the earliest blues music.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.