Iota, n.
Etymology: [L., fr. Gr. Jot.]
1. The ninth letter of the Greek alphabet (i) corresponding with the English i.
2. A very small quantity or degree; a jot; a particle. They never depart an iota from the authentic formulas of tyranny and usurpation. Burke. Iota subscript (Gr. Gram.), iota written beneath a preceding vowel, as a,, h,, w,, -- done when iota is silent.
Shades of meaning
Fernald has no entry of its own for iota; he lists it under particle.
He lists it without comment; the entries above explain its neighbors.