The Collaborative International Dictionary of English v.0.48:
Radical \Rad"i*cal\ (r[a^]d"[i^]*kal), 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
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
(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 flower.
4. (Philol.) Relating, or belonging, to the root, or ultimate
source of derivation; as, a radical verbal form.
5. (Math.) Of or pertaining to a radix or root; as, a radical
quantity; a radical sign. See below.
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;
Radical sign (Math.), the sign [root] (originally the
letter r, the initial of radix, root), placed before any
quantity, denoting that its root is to be extracted; thus,
[root]a, or [root](a + b). To indicate any other than the
square root, a corresponding figure is placed over the
sign; thus, [cuberoot]a, indicates the third or cube root
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 tissues.
Syn: Primitive; original; natural; underived; fundamental;
Usage: 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.