Is sloth the same thing as torpor?

When considering the 5 hindrances I always come across the tiredness hindrance translated as sloth and torpor. Since it is always (in my experience) translated as two words does the sloth and torpor hindrance embody two related but distinct phenomena? Is sloth somehow different to torpor? Is the original Pali two terms or is it just one concept that is just always translated as the two words - sloth and torpor.