( ( ( The ( longest ( technical word ) ) ) ( in English ) ) ( ( ( ( is ( ( the ( scientific name ) ) ( for ( the ( protein titin ) ) ) ) ) , ) ( at ( 189,819 letters ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJS longest) (JJ technical) (NN word)) (PP (IN in) (NP (NNP English)))) (VP (VBZ is) (NP (NP (DT the) (JJ scientific) (NN name)) (PP (IN for) (NP (DT the) (NN protein) (NN titin)))) (, ,) (PP (IN at) (NP (CD 189,819) (NNS letters)))) (. .)))
The longest technical word in English is the scientific name for the protein titin, at 189,819 letters.
(ROOT (S (NP (DT The) (ADJP (JJS largest) (VBN known)) (NNS proteins)) (VP (VBP are) (VP (VBN called) (NP (NNS titins)))) (. .)))