( ( The clouds ) ( ( are ( ( water droplets ) ( that ( form rain ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS clouds)) (VP (VBP are) (NP (NP (NN water) (NNS droplets)) (SBAR (WHNP (WDT that)) (S (VP (VBP form) (NP (NN rain))))))) (. .)))
The clouds are water droplets that form rain.
(ROOT (S (NP (NNS Clouds)) (VP (VBP are) (VP (VBN formed) (PP (IN from) (NP (NN water) (NNS droplets))))) (. .)))