Consider these examples: - cows eat grass - cows eating grass
What about "cows eating grass"? This noun phrase could be a
subject, but it has no predicate attached to it: the adjective
phrase "eating grass" show which cows the writer is referring
to, but there is nothing here to show why the writer is
mentioning cows in the first place. - cows eating grass are
visible from the highway This is a complete clause again. The
subject "cows eating grass" and the predicate "are visible from
the highway" make up a complete thought. This single-word
command is also a clause, even though it does seem to have a
subject. With a direct command, it is not necessary to include
the subject, since it is obviously the person or people you are
talking to: in other words, the clause really reads "[You]
run!". You should not usually use direct commands in your
essays, except in quotations. Written by David Megginson