Search for results excluding a word

To search for something excluding a certain word or phrase, use

grep -v "word" <file or location>

For example, the results of a grep search can include a lot of results which are not relevant. Eliminate those by using grep -v

 grep "blah" filename | grep -v "foo"

This will get you results with "blah" but nothing with "blah" and "foo" in them.