An Etymological Dictionary of Astronomy and Astrophysics
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Chem.: The -COOH group, regarded as the essential and characteristic constituent of organic acids.

From carb-, variant of carbo- before a vowel, from → carbon, + ox, from → oxygen, + -yl a suffix used in the names of radicals.

A diatomic chemical radical composed of carbon and nitrogen atoms. The triple bonds of C to H leave one electron available, which makes the CN radical very reactive. Organic molecules with the -CN group are potential sources of → prebiotic amino acids. Same as the → CN molecule. The CN radical was first identified by Gay-Lussac, who in 1815 published an extensive study of the derivatives of prussic acid (→ hydrogen cyanide). He showed that the cyano radical remained intact throughout a series of chemical transformations. Also called cyanogen radical.

→ cyano-; → radical.

A chemical radical that can exist independently from atoms or group of atoms.

→ free; → radical.

1) Math.: The indicated root of a quantity, as denoted by an expression written under the → radical sign.
2) Chemistry: A group of atoms present in a series of compounds which conserves its identity in the course of chemical changes which affect the rest of the molecule. For example, the → cyano radical and → hydroxyl group.

M.E., from L.L. radicalis "of or having roots," from → radix "root."

→ root.

Of two circles, the straight line containing all points P such that the lengths of the tangents from P to the two circles are equal.

→ radical; → axis.

The symbol √ placed before a number or quantity to indicate the extraction of the square root. The value of a higher (the n-th) root is indicated by a raised positive digit (n) in front of the symbol, as in ³√ (cube root). The first known occurrence of this symbol was in the book Die Cross, published in 1525, by the German mathematician Christoff Rudolff.

→ radical; → symbol.