/ Dictionary / Index F focal ratio: Meaning and Definition of Find definitions for: fo'cal ra"tio Pronunciation: [key] — Optics., Optics.,Photog. f-number. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. focal point focal seizure Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language