( ( An element ) ( ( is ( ( a substance ) ( that ( ( can not ) ( be ( ( ( broken down ) ( into ( other substances ) ) ) ( by ( ordinary ( chemical means ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NN element)) (VP (VBZ is) (NP (NP (DT a) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (RB not) (VP (VB be) (VP (VBN broken) (PRT (RP down)) (PP (IN into) (NP (JJ other) (NNS substances))) (PP (IN by) (NP (JJ ordinary) (NN chemical) (NNS means)))))))))) (. .)))
An element is a substance that cannot be broken down into other substances by ordinary chemical means.
(ROOT (S (NP (PRP You)) (VP (VBP call) (NP (NP (DT a) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (RB not) (VP (VB be) (VP (VBN broken) (PRT (RP down)) (PP (TO to) (NP (JJ other) (NNS substances))) (PP (IN by) (NP (NP (NN chemical) (NNS reactions)) (NP (DT an) (NN element))))))))))) (. .)))