( There ( ( ( ( ( is , ) however ) , ) ( ( a difference ) ( between ( ( the force ) ( of ( ( gravity and ) magnetism ) ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBZ is) (, ,) (ADVP (RB however)) (, ,) (NP (NP (DT a) (NN difference)) (PP (IN between) (NP (NP (DT the) (NN force)) (PP (IN of) (NP (NN gravity) (CC and) (NN magnetism))))))) (. .)))
There is, however, a difference between the force of gravity and magnetism.
(ROOT (S (NP (NNP Gravity) (CC and) (NNP magnetism)) (VP (VBP are) (NP (DT both) (JJ common) (NNS forces))) (. .)))
Gravity and magnetism are both common forces.