( Rain ( ( is ( defined ( as ( precipitation ( of ( drops ( of ( liquid water ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN Rain)) (VP (VBZ is) (VP (VBN defined) (PP (IN as) (NP (NP (NN precipitation)) (PP (IN of) (NP (NP (NNS drops)) (PP (IN of) (NP (JJ liquid) (NN water))))))))) (. .)))
Rain is defined as precipitation of drops of liquid water.
(ROOT (S (NP (NN Rain)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (JJ liquid) (NN water))))) (. .)))