title: Bleu_score in NLTK library
body: <p>I am new to using the nltk library. I want to find the two most similar strings. In doing so, I used the 'bleu_score' as follows:</p>
  <pre><code>import nltk
  from nltk.translate import bleu
  from nltk.translate.bleu_score import SmoothingFunction
  smoothie = SmoothingFunction().method4```
  
  
  C1 = 'FISSEN Ltds'
  C2 = 'FISSEN Ltds Maschinen- und Werkzeugbau'
  C3 = 'V.R.P. Baumaschinen Ltds'
  print('BLEUscore1:',bleu([C1], C2, smoothing_function=smoothie, auto_reweigh=False))
  print('BLEUscore2:',bleu([C2], C3, smoothing_function=smoothie, auto_reweigh=False))
  print('BLEUscore3:',bleu([C1], C3, smoothing_function=smoothie, auto_reweigh=False))
  </code></pre>
  <p>The output is like this:</p>
  <pre><code>BLEUscore1: 0.2585784506653774
  BLEUscore2: 0.26042143846335913
  BLEUscore3: 0.1472821272412462
  </code></pre>
  <p>I wonder why the results show the best similarity between C2 and C3 while C1 and C2 are the best answers. And what is the best way to assess this similarity between two strings whose answer is C1 and C2?</p>
  <p>I appreciate any help you can provide :)</p>