( ( ( Anion - ) ( ( An ion ) ( with ( ( ( a ( negative charge ) ) , ) ( formed ( when ( ( an ( atom gains ) ) ( electrons ( in ( a reaction ) ) ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (NNP Anion)) (: -) (NP (NP (DT An) (NN ion)) (PP (IN with) (NP (NP (DT a) (JJ negative) (NN charge)) (, ,) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (DT an) (NN atom) (NNS gains)) (VP (VBZ electrons) (PP (IN in) (NP (DT a) (NN reaction)))))))))) (. .)))
Anion- An ion with a negative charge, formed when an atom gains electrons in a reaction.
(ROOT (S (NP (NNS Anions)) (VP (VBP are) (VP (VBN formed) (PP (IN by) (NP (NP (NNS atoms)) (VP (VBG gaining) (NP (NNS electrons))))))) (. .)))