The spelling and pronunciation rules of Spanish are extremely consistent, and sometimes a conjugated form of the verb must change its spelling to maintain the correct pronunciation. This happens in the yo form of specific verbs in the preterite tense, because adding – í or – é to the base of the verb messes up the pronunciation of the word. The spelling change is meant to maintain the same basic sound as the infinitive.
Different Yo Forms in the Preterite Tense
Verbs that end in –gar
Remember that the consonant g is pronounced hard (like the g in good) or soft (like the g in gym) depending on the vowel that follows the g. If a Spanish verb ends in – gar, the infinitive is pronounced with a hard gsound. However, when you remove the – ar infinitive ending and add the yo preterite ending, the hard g is suddenly followed by – é and would be pronounced as a soft g. To maintain the hard g sound of the infinitive, the letter u is added between the g and é. This creates the hard g sound of the infinitive pronunciation.
Whenever you see a verb ending in – gué, you can assume the u is only there to produce the correct hard g sound, and you don't pronounce the u.
To simplify matters, remember that a verb ending in – gar will change g– to gu– in the yo form of the preterite. Table 1 is the preterite conjugation chart for the verb pagar (to pay) which serves as a good example. Note that the yo form would be pronounced [pah‐GAY].
The following verbs are all regular – ar verbs in the preterite tense. Since they all end in – gar, you must change the g to gu in the yo form and then use the regular yo ending. All other preterite forms of these verbs are completely regular forms for a regular – ar verb in the preterite tense.
Verbs that end in –car
The Spanish letter c is a lot like the letter g. It has a hard sound (like the English letter k) and a soft sound (like the English letter s). The c is pronounced soft when it's followed by –i or – e. It is pronounced hard when it's followed by – o, – a, or –u. Any verb that ends in – car will have the hard c sound in its infinitive form. This must be maintained in all the conjugated forms, but the preterite yo ending causes problems.
When you add – é to the base of a verb ending in – car, the c becomes a soft sound, which is unacceptable. So you must change the letter c to qu only in the yo preterite form. The resulting ending (– qué) is pronounced like the English name Kay. The combination of letters – qu is always pronounced like the English letter k, and you never say the u sound. It is never pronounced like the English word queen.
Table 2 is the preterite conjugation chart for the verb tocar (to play an instrument, to touch), which is an example for all regular – ar verbs in the preterite that end in – car.
To simplify the rule: If a verb ends in – car, change c to qu in the yo form of the preterite.
Here are some common verbs that end in – car, and they are all conjugated like tocar.
Verbs that end in –zar
Whenever z is followed by e, it changes to c. This rule becomes important in the preterite tense because the verbs that end in – zar will change spelling in the yo form. Since the yo form has the ending – é, the z must change to c. For example, Table 3 shows the preterite conjugation of the verb cruzar (to cross).
Here are some common verbs that end in – zar, and they are conjugated like cruzar.
I to y
When the stem of the verb ends in a vowel, some spelling changes are necessary in certain forms in the preterite. This special spelling change only happens in the preterite tense and is not considered a stem changer. If there are three vowels in a row and the middle one is the letter i, you must change the i to y. The preterite endings for – er and – ir verbs will cause the i>y spelling change to happen in the third person forms ( él, ella, usted, ellos, ellas, and ustedes), and an accent will be added to any other letter – i in the base of the verb in the conjugation chart.
Table 4 is a conjugation chart of the verb caer (to fall), which illustrates these changes. Consider the él form of the verb. If you simply added the ending –ió to the base of the verb ca–, the result would be caió. Since there are three vowels and the middle one is the letter i, it changes to y in the chart. Notice this also happens to the third person plural form of the verb.
Other verbs that have a base ending in a vowel are conjugated like caer. For example:
Table 5 shows the conjugation for the verb construir.
Here are some common – uir verbs that are all conjugated like construir: