The rarity of co-occurring every candidate word pair which possibly involves in a semantic relation leads us to exploit a method which does not necessarily need to see the word pair in a context together.
according to the distributional hypothesis which states "words that occur in similar contexts tend to have similar meanings" (Harris, 1954), distributional approaches try to recognize the relation between words based on their separate occurrence in the corpus which can be represented for example by their word embedding vectors (Mikolov et al.,2013) and these methods have shown great performance (Baroni et al., 2012;Turney and Pantel, 2010;Roller et al., 2014).