The longest official word ever (1,913 letters) is the term for the formula C₁₂₈₉H₂₀₅₁N₃₄₃O₃₇₅S₈

Methionyl­glutaminyl­arginyl­tyrosyl­glutamyl­seryl­leucyl­phenyl­alanyl­alanyl­glutaminyl­leucyl­lysyl­glutamyl­arginyl­lysy­glutamyl­gycyl­alanyl­phenyl­alanyl­valyl­prolyl­phenyl­alanyl­valyl­threonyl­leucyl­glycyl­aspartyl­prolyl­glycyl­isoleucyl­glutamyl­glutaminyl­seryl­leucyl­lysyl­isoleucyl­aspartyl­threonyl­leucyl­isoleucyl­glutamyl­alanyl­glycyl­alanyl­aspartyl­alanyl­leucyl­glutamyl­leucyl­glycyl­isoleucyl­prolyl­phenyl­alanyl­seryl­aspartyl­prolyl­leucyl­alanyl­aspartyl­glycyl­prolyl­threonyl­isoleucyl­glutaminyl­asparaginyl­alanyl­threonyl­leucyl­arginyl­alanyl­phenyl­alanyl­alanyl­alanyl­glycyl­valyl­threonyl­prolyl­alanyl­glutaminyl­cysteinyl­phenyl­alanyl­glutamyl­methionyl­leucyl­alanyl­leucyl­isoleucyl­arginyl­glutaminyl­lysyl­histidyl­prolyl­threonyl­isoleucyl­prolyl­isoleucyl­glycyl­leucyl­leucyl­methionyl­tyrosyl­alanyl­asparaginyl­leucyl­valyl­phenyl­alanyl­asparaginyl­lysyl­glycyl­isoleucyl­aspartyl­glutamyl­phenyl­alanyl­tyrosyl­alanyl­glutaminyl­cysteinyl­glutamyl­lysyl­valyl­glycyl­valyl­aspartyl­sryl­valyl­leucyl­valyl­alanyl­aspartyl­valyl­prolyl­valyl­glutaminyl­glutamyl­seryl­alanyl­prolyl­phenyl­alanyl­arginyl­glutaminyl­alanyl­alanyl­leucyl­arginyl­histidyl­asparaginyl­valyl­alanyl­prolyl­isoleucyl­phenyl­alanyl­isoleucyl­cysteinyl­prolyl­prolyl­aspartyl­alanyl­aspartyl­aspartyl­aspartyl­leucyl­leucyl­arginyl­glutaminyl­isoleucyl­alanyl­seryl­tyrosyl­glycyl­arginyl­glycyl­tyrosyl­threonyl­tyrosyl­leucyl­leucyl­seryl­arginyl­alanyl­glycyl­valyl­threonyl­glycyl­alanyl­glutamyl­asparaginyl­arginyl­alanyl­alanyl­leucyl­leucyl­lysyl­glutamyl­tyrosyl­asparaginyl­alanyl­alanyl­prolyl­prolyl­leucyl­glutaminyl­glycyl­phenyl­alanyl­glycyl­isoleucyl­seryl­alanyl­prolyl­aspartyl­glutaminyl­valyl­lysyl­alanyl­alanyl­isoleucyl­aspartyl­alanyl­glycyl­alanyl­alanyl­glycyl­alanyl­isoleucyl­seryl­glycyl­seryl­alanyl­isoleucyl­valyl­lysyl­isoleucyl­isoleucyl­glutamyl­glutaminyl­histidyl­asparaginyl­isoleucyl­glutamyl­prolyl­glutamyl­lysyl­methionyl­leucyl­alanyl­alanyl­leucyl­lysyl­valyl­phenyl­alanyl­valyl­glutaminyl­prolyl­methionyl­lysyl­alanyl­alanyl­threonyl­arginyl­serine.

Absolutely true.

Researcher's Note: Do you have any idea how long it took me to copy this down?