The best replacement for focal length is zoom.

The best alternatives to focal length are rated as following:
★★★★★  zoom
★★★★  magnification
★★★★  aperture
★★★  depth of field
★★★  angle of view
★★  shutter speed
★★  field of view
★★  focal point
★  fov
★  optical zoom
★  aperture telescope
★  working distance
★  focal plane
★  optical power
★  focal distance
★  image size
  radius of curvature
  image distance
  dof
  focus distance
  diopter
  distance from subject
  zoom power

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Speaking about focal length, one probably shouldn't forget about lens.

Other search terms related to focal length and their ratings are:
★★★★★ lens
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focal length
zoom
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