que cantaras

that you would sing

→ que
phrase Uncommon #19,307
that you would sing This is the imperfect subjunctive form used with tú. The example sentences also contain related forms: que cante means “that he/she sing” or “let him/her sing,” and que cantara means “that he/she sang” or “that he/she would sing.”
SP: No sabía que cantaras tan bien.
EN: I didn't know that you sang so well.