An 'appendage' in the broadest sense is an additional or subsidiary part existing on, or added to, something which can generally still function if the appendage has never existed or is later provided or grown, or will still perform a primary function if the appendage is removed.
Biological context
An 'appendage' is an external body part, or natural prolongation, that protrudes from an
organism's body, such as a
vertebrate's
limbs.
In
invertebrate biology, "'appendage'" is a general term that covers any of the
homologous body parts that may extend from a
body segment. These include
antennae,
mouthparts (including
mandibles,
maxillae and
maxillipeds),
wings,
elytra,
gills, walking
legs (
pereiopods), swimming legs (
pleopods), sexual organs (
gonopods), and parts of the tail (
uropods). Typically, each body segment carries one pair of appendages.
Appendages may be ''uniramous'', as in
insects and
centipedes, where each appendage comprises a single series of segments, or it may be ''biramous'', as in many
crustaceans, where each appendage branches into two sections. ''Triramous'' (branching into three) appendages are also possible.
All arthropod appendages are variations of the same basic structure (''homologous''), and which structure is produced is controlled by "
homeobox" genes. Changes to these genes have allowed scientists to produce animals (chiefly ''
Drosophila melanogaster'') with modified appendages, such as legs instead of antennae.
Linguistic context
In
British English, depending on the surrounding context, "appendage" might infer that the added words to which it refers give a more precise meaning to a name or description or else it might be used in a derogatory sense to describe an addition which appears to serve no useful function.