title: what is the difference between bigram and unigram text features extraction
body: <p>I searched online to do bi-gram and unigram text features' extraction, but still didn't find something useful information, can someone tell me what is the difference between them?</p>
  
  <p>For example, if I have a text "I have a lovely dog"
  what will happen if I use bi-gram way to do features extraction and to do unigram extraction?</p>