( ( A base ) ( ( is ( ( a substance ) ( that ( ( ( ( ( ( acts ( as ( a ( proton acceptor ) ) ) ) , ) ( produces ( ( hydroxide ions ) ( -LRB- ( ( OH - ) -RRB- ) ) ) ) ) , ) or ) ( ( serves ( as ( an ( electron donor ) ) ) ) ( when ( it ( is ( dissolved ( in water ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN base)) (VP (VBZ is) (NP (NP (DT a) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBZ acts) (PP (IN as) (NP (DT a) (NN proton) (NN acceptor)))) (, ,) (VP (VBZ produces) (NP (NP (JJ hydroxide) (NNS ions)) (PRN (-LRB- -LRB-) (NP (NNP OH) (NNP -)) (-RRB- -RRB-)))) (, ,) (CC or) (VP (VBZ serves) (PP (IN as) (NP (DT an) (NN electron) (NN donor))) (SBAR (WHADVP (WRB when)) (S (NP (PRP it)) (VP (VBZ is) (VP (VBN dissolved) (PP (IN in) (NP (NN water))))))))))))) (. .)))
A base is a substance that acts as a proton acceptor, produces hydroxide ions (OH-), or serves as an electron donor when it is dissolved in water.
(ROOT (S (NP (DT A) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN base)) (VP (VBZ is) (NP (NP (DT an) (JJ ionic) (NN compound)) (SBAR (WHNP (WDT that)) (S (VP (VBZ produces) (NP (JJ negative) (NN hydroxide) (NNS ions)) (SBAR (WHADVP (WRB when)) (S (VP (VBN dissolved) (PP (IN in) (NP (NN water)))))))))))))