Forward biasing of EBJ of npn BJT
Under the passive current convention, we say the current is positive when it flows in to a pin. So if this convention is followed, when the b-e junction of an NPN BJT is forward biased, the emitter current will be negative. 

However, not all engineers consistently use the passive current convention, so you often have to determine from context which direction is meant when a current (or voltage, for that matter) is given, either positive or negative.