F3

F3 is a designation used in several different fields, meaning not a single concept but multiple, context-dependent meanings. It appears in computing, genetics, astronomy, and meteorology, among others, reflecting its role as a generic label for a third item in a series or category.

In computing, F3 refers to the third function key on most keyboards. Pressing F3 commonly triggers a search or “find next” operation within many software programs, though the exact behavior can vary by application and some devices require an additional modifier key such as Fn.

In genetics and breeding, F3 denotes the third filial generation. This generation is produced by crossing individuals from the F2 generation and is used to study inheritance patterns, trait stability, and the fixation of characteristics over successive generations.

In astronomy, F3 designates a subclass within the F-type stellar classification. F-type stars are white and hotter than the Sun, and the numeral 3 specifies a finer temperature and spectral range within the broader F category, indicating properties that are intermediate among F0 to F9 stars.

In meteorology, F3 refers to a mid-range category on the original Fujita scale for tornado intensity, corresponding to estimated wind speeds around 158–206 mph (255–333 km/h). The Fujita scale has been superseded in the United States by the Enhanced Fujita (EF) scale since 2007, but historical references to F3 remain in use in some contexts.