As verbs the difference between expand and duplicate
is that
expand is (
label) to change (something) from a smaller form and/or size to a larger one while
duplicate is to make a copy of.
As an adjective duplicate is
being the same as another; identical this
may exclude the first identical item in a series, but usage is inconsistent.
As a noun duplicate is
one that resembles or corresponds to another; an identical copy.