appendage

n. something which is attached or added; supplement

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.
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Appendage /ap·pen·dage/ a subordinate portion of a structure, or an outgrowth, such as a tail. epiploic appendages see under appendix. [more]Appendage - Community and Resources

Noun
1. an external body part that projects from the body; "it is important to keep the extremities warm"
(synonym) extremity, member
(hypernym) external body part
(hyponym) chelicera
2. a natural prolongation or projection from a part of an organism either animal or plant; "a bony process"
(synonym) process, outgrowth
(hypernym) body part
(hyponym) horn
3. a part that is joined to something larger
(hypernym) part, portion
(hyponym) appendicle
(derivation) append, add on, supplement, affix

(n.)
Something appended to, or accompanying, a principal or greater thing, though not necessary to it, as a portico to a house.
  

(n.)
A subordinate or subsidiary part or organ; an external organ or limb, esp. of the articulates.