( We ( ( can ( ( define pressure ) ( as ( ( a force ) ( per ( unit area ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (MD can) (VP (VB define) (NP (NN pressure)) (PP (IN as) (NP (NP (DT a) (NN force)) (PP (IN per) (NP (NN unit) (NN area))))))) (. .)))
We can define pressure 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)))))))))) (. .)))