What is the difference between ellipsis and substitution?

What is the difference between ellipsis and substitution?
【正确答案】：Ellipsis is the set of resources by which full repetition of a clause or clause element can be avoided, and by which it can be signaled to readers that they should repeat the wording from a previous clause (or, in some cases, from their own knowledge).
Substitution refers to replacing the same word in one paragraph most often by one, do or so, in order to avoid repeating the same word several times.
Ellipsis works anaphorically by leaving out something mentioned earlier, whereas substitution works by substituting a “holding device” in the place of earlier elements.