1. Irregular Preterite Tense
The Triangle Verbs

2. What are Triangle Verbs
The triangle verbs are a set of irregular verbs that all share the same set of endings. The most common of these verbs are
Tener — Poner — Saber
Estar — venir — Querer
Poder — decir
Hacer — traer

3. The Endings imos iste isteis ieron
I use a triangle to help me remember the endings. The areas the triangle touches are identical to regular –er/-ir preterite tense endings.
imos
iste
isteis
ieron

4. The other endings e imos iste isteis o ieron
The other two endings I remember are just like the –ar preterite tense endings but without accents. e
imos
iste
isteis o
ieron

5. The Stems
Every triangle verb—in other words, all the verbs that use these endings—has an irregular stem. This means you will not be able to simply take the –ar, -er, and –ir off as you have done in the past.
YOU MUST MEMORIZE THE STEM AS WELL AS THE ENDINGS.

6. These are the Stems Tener  tuv Poner  pus Saber  sup Estar  estuv
Venir vin
Querer  quis
Poder  pud
Decir  dij
Hacer  hic/z
Traer  traj

7. Putting it all together
The endings
The conjugation process e
imos
iste o
ieron
First choose the verb that communicates the meaning you want
Select the irregular stem for that verb.
Add the ending that matches the doer of the action.

8. Let’s conjugate poder to say “he could.”
imos
iste
ieron
First, write the stem for poder
PUD
Second, add the he/she/usted ending from the irregular set of endings. O o

9. The process is the same with other triangle verbs
To conjugate hacer to “we made” we would write the irregular stem.
And then add the we form ending. e
iste o
ieron
imos
Hic
imos

10. Two Special Rules
The verb hacer uses the irregular stem “HIC.” The he/she/Ud. ending is an “O.” Because the “C” will change pronunciation when followed by “O,” we change the “C” to a “Z.”
HIZO
Stems that end in “J” such as “traj” and “dij” will drop the “I” in the ellos/Uds. form.
If the stem ends in “j” drop the “i” in they.
TRAJERON
DIJERON

11. All that is left is to memorize
You should memorize this using the method that works best for you. If you like rules, follow the ones in this presentation.
If you prefer to simply memorize, take some time and write out the conjugations and study them until they are automatic.