What is a matrix clause?

The source below says this about a clauses in
gneneral.

readability="9.113475177305">

"One clause may be
embedded within another, that is, it may be used as a
constituent part of another clause. Such a clause is called an embedded
clause (or a href="http://grammar.about.com/od/rs/g/subclterm.htm">subordinate clause)
and the clause within which it is embedded is called the href="http://grammar.about.com/od/mo/g/matrixclauseterm.htm">matrix
clause. The embedded clause is a constituent of the matrix clause.
A clause that could occur on its own as a href="http://grammar.about.com/od/rs/g/senterm.htm">sentence is called a
main clause.
In the following examples the embedded clauses are given in boldface; each of the matrix
clauses is also a main clause: The boy who came
is his cousin. I told him that I would
go.

To
explain this again, the matrix clause is an independent clause that could stand on its
own and make perfect sense.  It is called a matrix clause when there are subordinate
clauses in the sentence as well.  Subordinate clauses can appear anywhere in a sentence
so it is important to note the subordinating conjunction or relative pronoun that
usually introduces them if you are trying to identify the distinct clauses that make up
a complete sentence.  In the example sentences above, "who" is a relative
pronoun/subject of the verb "came."  That clause can't stand alone -- it is subordinate
to the rest of the sentence -- it is part of the idea, but not the whole idea.  In the
other example, "that" is is a subordinating conjunction introducing a subordinate
clause.  Again, that part of the sentence can't stand alone, but provides more
information and completes the thought of the independent (matrix) part of the
sentence.