( ( ( a insulator ) ( is ( something ( that ( ( ( is ( ( a barrier ) ( to electrons ) ) ) and ) ( ( can not ) ( pass electricity ) ) ) ) ) ) ) ( , ( rubber ( ( is ( a ( good insulator ) ) ) . ) ) ) )
(ROOT (S (S (NP (DT a) (NN insulator)) (VP (VBZ is) (NP (NP (NN something)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBZ is) (NP (NP (DT a) (NN barrier)) (PP (TO to) (NP (NNS electrons))))) (CC and) (VP (MD can) (RB not) (VP (VB pass) (NP (NN electricity)))))))))) (, ,) (NP (NN rubber)) (VP (VBZ is) (NP (DT a) (JJ good) (NN insulator))) (. .)))
a insulator is something that is a barrier to electrons and can not pass electricity, rubber is a good insulator.
(ROOT (S (NP (NNP Rubber)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (NP (DT a) (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-) (NNS insulators)) (SBAR (WHNP (WDT that)) (S (VP (VBZ does) (RB not) (VP (VB allow) (S (NP (NNS electrons)) (VP (TO to) (VP (VB move) (PP (IN through) (NP (PRP them)))))))))))))) (. .)))