a. [F., fr. L. radicalis having roots, fr.
radix, -icis, a root. See Radix.]
1. Of or pertaining to the root; proceeding
directly from the root.
2. Hence: Of or pertaining to the root or
origin; reaching to the center, to the foundation, to the ultimate
sources, to the principles, or the like; original; fundamental;
thorough-going; unsparing; extreme; as, radical evils;
radical reform; a radical party.
The most determined exertions of that authority,
against them, only showed their radical
3. (Bot.) (a) Belonging
to, or proceeding from, the root of a plant; as, radical tubers
or hairs. (b) Proceeding from a rootlike
stem, or one which does not rise above the ground; as, the
radical leaves of the dandelion and the sidesaddle
4. (Philol.) Relating, or belonging, to
the root, or ultimate source of derivation; as, a radical
5. (Math.) Of or pertaining to a radix
or root; as, a radical quantity; a radical sign. See
Radical axis of two circles. (Geom.)
See under Axis. -- Radical pitch,
the pitch or tone with which the utterance of a syllable
begins. Rush. -- Radical quantity
(Alg.), a quantity to which the radical sign is prefixed;
specifically, a quantity which is not a perfect power of the degree
indicated by the radical sign; a surd. -- Radical
sign (Math.), the sign √ (originally the
letter r, the initial of radix, root), placed before any
quantity, denoting that its root is to be extracted; thus,
√a, or √(a + b). To indicate any
other than the square root, a corresponding figure is placed over the
sign; thus, ∛a, indicates the third or cube root of
a. -- Radical stress (Elocution),
force of utterance falling on the initial part of a syllable or
sound. -- Radical vessels (Anat.),
minute vessels which originate in the substance of the
Syn. -- Primitive; original; natural; underived;
fundamental; entire. -- Radical, Entire. These words
are frequently employed as interchangeable in describing some marked
alteration in the condition of things. There is, however, an obvious
difference between them. A radical cure, reform, etc., is one
which goes to the root of the thing in question; and it is
entire, in the sense that, by affecting the root, it affects in
an appropriate degree the entire body nourished by the root;
but it may not be entire in the sense of making a change
complete in its nature, as well as in its extent. Hence, we speak of a
radical change; a radical improvement; radical
differences of opinion; while an entire change, an
entire improvement, an entire difference of opinion,
might indicate more than was actually intended. A certain change may
be both radical and entire, in every sense.
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
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.
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
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