Can you explain what you mean by 'delimited?'

I just copied the NeoOffice file (saved as .doc, a word format) to text edit (a .txt file) and the command worked (grep 'I am writing') but it printed the whole letter, or most of it -- which I'm guessing means that it found all the lines with any of the three words in the string and printed those lines. Is it possible to use 'grep' to find this particular sentence fragment and no other lines which don't contain this entire fragment?