その少年は賢いことがわかった。

that (something or someone distant from the speaker, close to the listener; actions of the listener, or ideas expressed or understood by the listener); the; um...; er...; uh...

boy; juvenile; young boy; youth; lad

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

wise; clever; smart

thing; matter; incident; occurrence; event; something serious; trouble; crisis; circumstances; situation; state of affairs; work; business; affair; after an inflectable word, creates a noun phrase indicating something the speaker does not feel close to; nominalizing suffix; pretending to ...; playing make-believe ...; alias; aka; nickname; alternative name; also known as

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

to understand; to comprehend; to grasp; to see; to get; to follow; to become clear; to be known; to be discovered; to be realized; to be realised; to be found out