( ( A weed ) ( ( can ( be ( defined ( as ( ( any plant ) ( that ( grows ( where ( it ( ( is not ) wanted ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN weed)) (VP (MD can) (VP (VB be) (VP (VBN defined) (PP (IN as) (NP (NP (DT any) (NN plant)) (SBAR (WHNP (WDT that)) (S (VP (VBZ grows) (SBAR (WHADVP (WRB where)) (S (NP (PRP it)) (VP (VBZ is) (RB not) (VP (VBN wanted))))))))))))) (. .)))
A weed can be defined as any plant that grows where it is not wanted.
(ROOT (S (NP (NNS Weeds)) (VP (VBP are) (NP (NP (NNS plants)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBP grow) (SBAR (WHADVP (WRB where)) (S (NP (NNS people)) (VP (VBP do) (RB n't) (VP (VB want) (NP (PRP them)) (PP (TO to))))))) (CC and) (VP (MD can) (VP (VB take) (PRT (RP up)) (NP (NP (NN space) (CC and) (NN use) (NNS resources)) (SBAR (WHNP (WDT which)) (S (VP (VBZ hinders) (NP (NP (NN growth)) (PP (IN of) (NP (ADJP (RBR more) (JJ desirable)) (NNS plants))))))))))))))) (. .)))