Rad·i·cal n.
 1. Philol. (a) A primitive word; a radix, root, or simple, underived, uncompounded word; an etymon. (b) A primitive letter; a letter that belongs to the radix.
    The words we at present make use of, and understand only by common agreement, assume a new air and life in the understanding, when you trace them to their radicals, where you find every word strongly stamped with nature; full of energy, meaning, character, painting, and poetry.   --Cleland.
 2. Politics One who advocates radical changes in government or social institutions, especially such changes as are intended to level class inequalities; -- opposed to conservative.
    In politics they [the Independents] were, to use the phrase of their own time, =\“Root-and-Branch men,” or, to use the kindred phrase of our own, Radicals.\=   --Macaulay.
 3. Chem. (a) A characteristic, essential, and fundamental constituent of any compound; hence, sometimes, an atom.
    As a general rule, the metallic atoms are basic radicals, while the nonmetallic atoms are acid radicals.   --J. P. Cooke.
 (b) Specifically, a group of two or more atoms, not completely saturated, which are so linked that their union implies certain properties, and are conveniently regarded as playing the part of a single atom; a residue; -- called also a compound radical.  Cf. Residue.
 4. Alg. A radical quantity. See under Radical, a.
    An indicated root of a perfect power of the degree indicated is not a radical but a rational quantity under a radical form.   --Davies & Peck (Math. Dict.)
 5. Anat. A radical vessel. See under Radical, a.

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 Com·pound a.  Composed of two or more elements, ingredients, parts; produced by the union of several ingredients, parts, or things; composite; as, a compound word.
    Compound substances are made up of two or more simple substances.   --I. Watts.
 Compound addition, subtraction, multiplication, division Arith., the addition, subtraction, etc., of compound numbers.
 Compound crystal Crystallog., a twin crystal, or one seeming to be made up of two or more crystals combined according to regular laws of composition.
 Compound engine Mech., a form of steam engine in which the steam that has been used in a high-pressure cylinder is made to do further service in a larger low-pressure cylinder, sometimes in several larger cylinders, successively.
 Compound ether. Chem. See under Ether.
 Compound flower Bot., a flower head resembling a single flower, but really composed of several florets inclosed in a common calyxlike involucre, as the sunflower or dandelion.
 Compound fraction. Math. See Fraction.
 Compound fracture. See Fracture.
 Compound householder, a householder who compounds or arranges with his landlord that his rates shall be included in his rents. [Eng.]
 Compound interest. See Interest.
 Compound larceny. Law See Larceny.
 Compound leaf Bot., a leaf having two or more separate blades or leaflets on a common leafstalk.
 Compound microscope. See Microscope.
 Compound motion. See Motion.
 Compound number Math., one constructed according to a varying scale of denomination; as, 3 cwt., 1 qr., 5 lb.; -- called also denominate number.
 Compound pier Arch., a clustered column.
 Compound quantity Alg., a quantity composed of two or more simple quantities or terms, connected by the sign + (plus) or - (minus). Thus, a + b - c, and bb - b, are compound quantities.
 Compound radical. Chem. See Radical.
 Compound ratio Math., the product of two or more ratios; thus ab:cd is a ratio compounded of the simple ratios a:c and b:d.
 Compound rest Mech., the tool carriage of an engine lathe.
 Compound screw Mech., a screw having on the same axis two or more screws with different pitch (a differential screw), or running in different directions (a right and left screw).
 Compound time Mus., that in which two or more simple measures are combined in one; as, 6-8 time is the joining of two measures of 3-8 time.
 Compound word, a word composed of two or more words; specifically, two or more words joined together by a hyphen.