In
mathematics, a
subsequence is a
sequence that can be derived from another sequence by deleting some elements without changing the order of the remaining elements. For example, the sequence
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=2096)
is a subsequence of
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=1950)
. They should not be confused with
substring which is for above string and which is a refinement of subsequence. The relation of one sequence being the subsequence of another is a
preorder.