tear

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tear

a drop of the secretion of the lacrimal glands
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Tear

 

a drop of the clear, slightly opalescent fluid secreted by the lacrimal glands. Tears are slightly alkaline. They contain as much as 99 percent water and 0.9 percent inorganic matter, chiefly sodium chloride and small quantities of sodium carbonate, magnesium carbonate, calcium sulfate, and calcium phosphate, as well as the antibacterial enzyme lysozyme; other proteins constitute 0.1 percent. Tears moisten the anterior surface of the eye and prevent it from drying, wash foreign bodies out of the conjunctival sac, and participate in the nutrition of the cornea.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

run

run, 3
1. In roofing, the horizontal distance from the face of a wall to the ridge of the roof.
2. In stairways, the width of a single stair tread.
3. The horizontal distance covered by a flight of steps.
4. The runway or track for a sash.
5. A small stream of paint flowing vertically on a
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.