[ foh-sahy, -kahy ]
See synonyms for foci on
  1. a plural of focus.

Words Nearby foci Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use foci in a sentence

  • In an orbit made elliptical by the planetary attraction the sun necessarily occupies one of the foci of the ellipse.

    Outlines of the Earth's History | Nathaniel Southgate Shaler
  • That an ellipse may be given any required proportion of width to length by locating the foci at the requisite distance apart.

  • That the proportion of length to width in an ellipse is determined by the distance apart of the foci.

  • The curve thus traced will be an ellipse having the pins at the two points which are called its foci.

    A Text-Book of Astronomy | George C. Comstock
  • These are at points on the principal axis that are twice as far from O, the center of the lens, as are the principal foci.

    Physics | Willis Eugene Tower