Expect value

The Expect Value (E) is the number of hits that a person would expect by chance when searching a database. The lower this value is, the higher the Score (S) of the match is. The closer the E-value gets to zero, the better the match is

The lower the E-value, or the closer it is to zero, the more "significant" the match is. But another factor that affects the E-value is the length of query. Since shorter ones have a higher chance of occurring in the database, they tend to have a higher E-value .