( Urine ( ( is ( ( a liquid ) ( that ( is ( ( formed ( by ( the kidneys ) ) ) ( when ( they ( ( filter wastes ) ( from ( the blood ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Urine)) (VP (VBZ is) (NP (NP (DT a) (NN liquid)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (VP (VBN formed) (PP (IN by) (NP (DT the) (NNS kidneys))) (SBAR (WHADVP (WRB when)) (S (NP (PRP they)) (VP (VBP filter) (NP (NNS wastes)) (PP (IN from) (NP (DT the) (NN blood)))))))))))) (. .)))
Urine is a liquid that is formed by the kidneys when they filter wastes from  the blood.
(ROOT (S (NP (NNP Urine)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (NP (JJ liquid) (NN waste)) (VP (VBN formed) (PP (IN by) (NP (NNS kidneys)))))))) (. .)))