"focal" - key terms from Wikipedia

actual focal	length
all focal	lengths
back focal
back focal	plane
effective focal	length
fixed focal	length
flange focal	distance
focal
focal	adhesion
focal	character
focal	depth
focal	distance
focal	epilepsy
focal	grave
focal	length
focal	length multiplier
focal	length of a lens
focal	length of the eyepiece
focal	lesions
focal	line
focal	neurologic
focal	plane
focal	plane array
focal	plane is located
focal	plane shutter
focal	point
focal	press
focal	range
focal	ratio
focal	segmental glomerulosclerosis
focal	seizures
focal	surface
front focal
front focal	plane
front focal	plane reticles
lens focal	length
long focal	length
longer focal	length lenses
position of the focal	plane
rear focal	plane
shorter focal