This parameter, which stands for "expect value", describes the number of hits one can "expect" to see by chance when searching a database of a particular size. It decreases exponentially with score. Essentially, the e-value describes the random background noise that exists for matches between sequences. For example, an e-value of 1 assigned to a hit can be interpreted as meaning that in a database of the current size, one might expect to see one match with a similar score simply by chance. The lower the e-value, the higher the "significance" of the match. However, searches with short sequences can be virtually identical and also have a relatively high e-value.