"Han säger inte ett ord."

Translation: He does not say a word.

[Sven_Larsen]

"He says not a word." is a common English phrase, but not accepted by Duolingo.

[devalanteriel]

That construction used to not be used in the course in the beginning. It was added later, but since it has to be added manually for every single applicable sentence, it's still missing in places. Please do report it using the "Report a problem" button whenever you encounter it.

[Ryn-Garingaroses]

Is "He doesn't say one word" a valid translation here as well? It would be okay in English to say both so I was just curious.

[devalanteriel]

Sure, that'd work.

[fl1cka]

Why not "He says not one word"

[devalanteriel]

Added that now.