About Daggers and knives

A dagger is a double-edged blade used for hitting, stabbing or thrusting. They often fulfill the role of a secondary defense weapon in close combat. In most cases, a tang extends into the handle along the centreline of the blade.
Daggers may be differentiated from knives on the basis that daggers are intended primarily for stabbing whereas knives are usually single-edged and intended mostly for cutting. However, many knives and daggers are capable of either stabbing or cutting.

Source: Wikipedia