(New notes at top; old below)


           Mi madre quiere que yo estudie más.

           No es posible que ella tenga 30 años.

           ¿Esperas que yo venga tarde?
           Es probable que nieve mañana.

           Ellos dudan que hables alemán.

           No es cierto que Pablo compre un coche.

           Siento que María esté enferma.


Preterite tense is the simple (one-word in English) past.  The preterite refers to an action completed in the past:
I ate an apple.
Comí una manzana.
(The apple is gone.) 
He read the book.
Él leyó el libro.
(He finished reading the book.)

Imperfect tense is a compound (more than one word in English) past.  The imperfect refers to the middle (after the beginning, before the end) but while the action was on-going.  NOTE!  The action most likely was completed at some point, but the speaker’s interest is in the middle.  Most often this type of action is expressed “was/were talking (eating, driving), but ¡OJO!, some people use the simple past here when they actually are referring to the middle.
I was sleeping at 8 AM. 
Yo dormía a las 8. 
(I went to sleep before 
     8, and woke up after 8.) 
They were studying....
Ellos estudiaban....
(I don’t know when they 
started or finished.)

The imperfect tense is also used for repeated actions (used to have, would drive) in the past.  ¡OJO!, some people use the simple past here when they actually are referring to a repeated action.
I used to visit (would visit) my grandmother almost every Sunday.
Yo visitaba a mi abuela casi todos los domingos.
(Even without “almost every Sunday”, visitaba tells you it was a 
     repeated action.)

Preterite and Imperfect in the same sentence.
Often the two tenses can be combined with each other.
While Sam was in the room, I ate an apple.
Mientras Sam estaba en el cuarto, comí una manzana.
(The apple got eaten while Sam was there, but I don’t care when 
     he arrived or left.)
I was sleeping at 8 AM when Beatriz called (phoned) me.
Yo dormía a las 8 de la mañana, cuando Beatriz me llamó.
(My sleeping, which was in progress before 8, was interrupted 
     by the phone call.)
Carlos read War and Peace while he was in the 9th grade.
Carlos leyó La guerra y la paz mientras estaba en el noveno 
(He was in the 9th grade both before and after he started and
     finished the book.)

Multiple preterite verbs or multiple imperfect verbs in the same sentence.
A series of either preterite or imperfect verbs can be used in one sentence.
I got up at 7, showered, got dressed, ate breakfast and left the 
     house at 9.
Yo me levanté a las 7, me duché, me vestí, desayuné, y salí de la 
     casa a las 9.
 (Each action got completed before the next one began.)
The other day while I was washing the dishes, my husband 
     was repairing a lamp.
El otro día mientras yo lavaba los platos, mi esposo reparaba una 
(Two actions were on-going at the same time. It’s not important 
     who got done first.)

“State” verbs (or verbs that represent a pre-existing condition)
There is a group of verbs that represents actions that do not generally have a clear beginning or end.  These verbs tend to be ones of being, feeling, seeming, wanting etc.  ALWAYS use the imperfect tense with the following verbs, unless a clear beginning or end is evident.

ser saber necesitar
tener  estar conocer
parecer ir a (+INF) poder
desear deber llamarse
sentirse querer acabar de (+INF)
hacer (weather) creer gustar
haber (there was)

The person in the room was Joe Edwards, my cousin.
La persona en el salón era Joe Edwards, mi primo.
(He was Joe Edwards before he went into the room, too.)
My third grade teacher was named “Miss Alma”.
Mi maestra del tercer grado se llamaba «Doña Alma».
(Her name was “Miss Alma” before I ever had her as a teacher.)
I was seven years old when I learned to ride a bike.
Yo tenía 7 años cuando aprendí a montar a bicicleta.
(I was 7 yrs. old all during that time; however, I finished learning 
     to ride then.)
I was going to go to Hawaii with my family, but then I broke my 
Yo iba a ir a Hawaii con mi familia, pero entonces me fracturé el 
(Breaking my ankle interrupted my intention of going, so “I was 
     going to go...”.)
It was warm yesterday when we were walking home.
Hacía calor ayer cuando caminábamos a casa.
(It was warm before you were walking home, too.  The heat didn’t 
     begin suddenly.)
I called my parents to tell them that I wanted to spend the 
     weekend in Duluth
Llamé a mis padres para decirles que yo quería pasar el fin de 
     semana en Duluth.
(Your desire to go to Duluth pre-existed your call.)
I needed to go to the doctor because I was sick.
Yo necesitaba ir al médico porque yo estaba enfermo.
(The need to go to the doctor pre-existed the actual call.  You 
     were sick before, too.)
Mary had just left when I arrived.
María acababa de salir cuando yo llegué.
(She “was finishing” leaving when I arrived.  I might even have 
     seen her go.)