( Pressure ( ( is ( ( the amount ) ( of ( ( force acting ) ( per ( unit area ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN Pressure)) (VP (VBZ is) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN force) (VBG acting)) (PP (IN per) (NP (NN unit) (NN area))))))) (. .)))
Pressure is the amount of force acting per unit area.
(ROOT (S (NP (NN Pressure)) (VP (VBZ is) (VP (VBN defined) (PP (IN in) (NP (NN physics))) (PP (IN as) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN force)) (VP (VBG pushing) (PP (IN against) (NP (DT a) (VBN given) (NN area)))))))))) (. .)))