yo sabía que no se iba a acostar hasta que Tom (no) volviera

ən'til
I ʌn'tɪl, ən'tɪl
II
[ǝn'tɪl] UNTIL ► As with other time conjunctions, has ta que is used with the {subjunctive} if the action which follows hasn't happened yet or hadn't happened at the time of speaking:
Go on stirring until the sauce is cold Sigue removiendo hasta que se enfríe la salsa
I shan't be happy until you come No estaré contenta hasta que (no) vengas When the main clause is negative, no can optionally be given in the hasta que clause without changing the meaning. ► Has ta que is used with the {indicative} when the action in the hasta que clause has already taken place:
He lived in this house until he died Vivió en esta casa hasta que murió
I didn't see her again until she returned to London No volví a verla hasta que (no) regresó a Londres ► Has ta que is also used with the {indicative} when describing habitual actions:
I never wake up until the alarm goes off Nunca me despierto hasta que (no) suena el despertador ► Instead of has ta que + ((verb)), you can use hasta with an {infinitive} when the subject of both clauses is the same:
Go on stirring until you get a thick creamy mixture Sigue removiendo hasta obtener una crema espesa For further uses and examples, see main entry
I [ʌn'tɪl, ən'tɪl]
II