Can grep show only words that match search pattern?

Question

Is there a way to make grep output \"words\" from files that match the search expression?

If I want to find all the instances of, say, \"th\" in a number of files, I

Answer 1

$ grep -w

Excerpt from grep man page:

-w: Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character.