1. A method comprising: receiving a collection of phrases from a collection of text, each phrase including two or more words; and for each phrase, determining if the phrase is a non-compositional compound, a non-compositional compound being a phrase of two or more words where the words composing the phrase have different meanings in a compound than their conventional meanings individually, the determining including: identifying a similar word for a word of the phrase, substituting the similar word for the word of the phrase to generate a substitute phrase, calculating a similarity between the phrase and the substitute phrase, including performing a similarity measure based on a context of the phrase and the substitute phrase, respectively, in the collection of text, and identifying the phrase as a non-compositional compound based on a comparison of the calculated similarity with a specified threshold.