For instance, despite the fact that the sentences "he is affected by AIDS" and "HIV is a virus" express concepts closely related, their similarity is zero in the VSM because they have no words in common (they are represented by orthogonal vectors).
due to the ambiguity of the word "virus" , the similarity between the sentences "the laptop has been infected by a virus" and "HIV is a virus" is greater than zero, even though they convey very different messages.