| Definition -
A clause that is used to restrict the meaning of another clause.
They are usually introduced by terms such as: i.e., in that, in so far as, that is to say, and inasmuch as.
For example: "He often took a leftist-Libertarian stance, i.e. he didn't make any sense."
As opposed to a restrictive relative clause, which is a clause that helps to precisely identify the sentence's subject.
For example, in the sentence The automobile that is in the tree is mine, the restrictive relative clause that is in the tree identifies which car is being discussed.