While both retinol and Retin-A contain retinoids, they differ in their concentration. Retinol and other forms, such as retinal and retinyl palmitate are found in many over-the-counter anti-aging creams. While these all contain a form of vitamin A, the concentration of retinoids is weak. Retin-A is a prescription retinoid and is a brand name for tretinoin, which is the carboxylic acid form of vitamin A and was one of the early topical acne treatments. Retin-A is sold by prescription because its acid composition is much greater than in over-the-counter products.
LINE (an undefined term) In geometry, a line has no thickness but its length extends in one dimension and goes on forever in both directions. A line is depicted to be a straight line with two arrowheads indicating that the line extends without end in two directions.
Full Definition of AMBIGUITY. 1. a: the quality or state of being ambiguous especially in meaning (see ambiguous) b: a word or expression that can be understood in two or more possible ways: an ambiguous word or expression.2. : uncertainty.See ambiguity defined for English-language learners.ull Definition of AMBIGUITY. 1. a: the quality or state of being ambiguous especially in meaning (see ambiguous) b: a word or expression that can be understood in two or more possible ways: an ambiguous word or expression. 2. : uncertainty. See ambiguity defined for English-language learners.