a. [f. as prec. + -AL.]
1. Of a line: Returning into itself so as to form a closed curve. rare.
1817. Coleridge, Biog. Lit., 122. [The point] must flow back again on itself; that is, there arises a cyclical line which does inclose a space.
b. Of a letter: Circular, encyclical. rare.
1879. Farrar, St. Paul, I. 434. The genuineness of this cyclical letter is evinced by its extreme naturalness.
2. = CYCLIC 1.
1825. Coleridge, On Prometheus (W.). Time, cyclical time, was their abstraction of the Deity.
1837. Sir F. Palgrave, Merch. & Friar, iii. (1844), 78. Modes of thought, not cyclical, but successive.
1854. Moseley, Astron., lxxix. (ed. 4), 219. The changes of the planetary orbits must return in certain cyclical periods.
1861. E. Smith (title), Health and Disease, as influenced by the Daily, Seasonal, and other Cyclical Changes in the Human System.
b. Belonging to a definite chronological cycle.
1838. Arnold, Hist. Rome, I. xviii. 382. The truce … was to last only for forty cyclical years of ten months each.
1875. Jowett, Plato (ed. 2), III. 579. Plato also speaks of an ‘annus magnus’ or cyclical year.
3. = CYCLIC 2.
1841. De Quincey, Homer, Wks. VI. 293. The many epic and cyclical poems which arose during post-Homeric ages.
1873. Symonds, Grk. Poets, vii. 191. The Cyclical poets.
4. Bot. a. Rolled up circularly, as the embryos of many seeds. b. Arranged in whorls, verticillate; hence transf. in Zool.
1866. in Treas. Bot.
1870. Hooker, Stud. Flora, 36. Wart-cress … embryo in some species cyclical.
1881. W. B. Carpenter, Microscope, 546. We find in the nautiloid spire a tendency to pass … into the cyclical mode of growth.
5. Cyclical number: (see quot.).
1875. Jowett, Plato (ed. 2), III. 113. A perfect or cyclical number…; i. e. a number in which the sum of the divisors equals the whole.
