( Pressure ( ( is ( ( the amount ) ( of ( force ( per ( unit area ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN Pressure)) (VP (VBZ is) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN force)) (PP (IN per) (NP (NN unit) (NN area))))))) (. .)))
Pressure is the amount of force 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)))))))))) (. .)))