Learn Italian: L'amico tradì il cavaliere nella battaglia. - The friend betrayed the knight in the battle.

The infinitive is tradire (to betray). This is the passato remoto (historical past) tense. For regular -ire verbs in the third person singular (he/she/it), you drop the -ire and add -ì.

Why is there an accent mark on tradì?

In the passato remoto, the third person singular forms for regular -are and -ire verbs always end with an accented vowel (-ò and -ì). This written accent tells you that the spoken stress falls on the very last syllable.

How would you change this sentence if multiple friends betrayed the knight?

You would change the subject and verb to say Gli amici tradirono il cavaliere. In the passato remoto, the third person plural (they) ending for regular -ire verbs is -irono.

Why use tradì here instead of the more common past tense, ha tradito?

The passato remoto is typically used in literature, historical accounts, or storytelling to describe actions completed in the distant past with no ongoing connection to the present. A sentence about knights and battles is a classic example of when you would encounter this tense!