- flat extension
- flat F-bundle
- flat field
- flat field apochromatic lens
- flat field correction
- flat fielding
- flat field photometry
- flatfishes
- flatfish metamorphosis
- flat flame kiln
- flat foot
- flat form
- flat function
- flat function germ
- flat glass
- flat graph
- flathead grey mullet
- flat holomorphic mapping
- flat ideal
- flat interferometer
- flat knitting machine
- flat knitting machine head
- flat knitting shaped shoe materials
- flat knitting sweater
- flat lapping block