Two, n.
1. The sum of one; the number next greater than one, and next less than three; two units or objects.
2. A symbol representing two units, as 2, II., or ii. In two, asunder; into parts; in halves; in twain; as, cut in two.
1 other Webster entry under this spelling
Two, a.
One and one; twice one. "Two great lights." Gen. i. 16. "Two black clouds." Milton.
Note: Two is often joined with other words, forming compounds signifying divided into, consisting of, or having, two parts, divisions, organs, or the like; as two-bladed, two-celled, two-eared, two-flowered, twohand, two-headed, two-horse, two-leafed or two- leaved, two-legged, two-lobed, two-masted, two-named, two-part, two- petaled, two-pronged, two-seeded, two-sided, two-story, two-stringed, two-foothed, two-valved, two-winged, and the like. One or two, a phrase often used indefinitely for a small number.
Shades of meaning
Fernald has no entry of its own for two; he lists it under both.
Where he writes about it:
Both refers to two objects previously mentioned, or had in mind, viewed or acting in connection; as, both men fired at once; "two men fired" might mean any two, out of any number, and without reference to any previous thought or mention. — from both
Twain is a nearly obsolete form of two. — from both
We would say both men rushed against the enemy; the two men flew at each other. — from both