FD

FD or similar may refer to:

==Science and technology== Canon FD lens mount, a standard for connecting a lens to a camera Familial dysautonomia, a disorder of the autonomic nervous system Fermi–Dirac statistics (F–D statistics), in quantum statistics Ferredoxin, iron–sulfur proteins File descriptor, in Unix and related computer operating systems Freedesktop.org (fd.o), an interoperability project Functional dependency, a constraint in a relation from a database Nissan FD engine, for trucks and buses