( ( When ( ( an alloy ) ( is ( called Bronze ) ) ) ) ( , ( it ( usually ( ( means ( ( the alloy ) ( of ( ( copper and ) tin ) ) ) ) . ) ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (DT an) (NN alloy)) (VP (VBZ is) (VP (VBN called) (NP (NN Bronze)))))) (, ,) (NP (PRP it)) (ADVP (RB usually)) (VP (VBZ means) (NP (NP (DT the) (NN alloy)) (PP (IN of) (NP (NN copper) (CC and) (NN tin))))) (. .)))
When an alloy is called Bronze, it usually means the alloy of copper and tin.
(ROOT (S (NP (NN Bronze)) (VP (VBZ is) (NP (NP (DT an) (NN alloy)) (PP (IN of) (NP (NN copper) (CC and) (NN tin))))) (. .)))