( Pressure ( ( is ( defined ( as ( ( a force ) ( per ( unit area ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN Pressure)) (VP (VBZ is) (VP (VBN defined) (PP (IN as) (NP (NP (DT a) (NN force)) (PP (IN per) (NP (NN unit) (NN area))))))) (. .)))
Pressure is defined as a 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)))))))))) (. .)))