Irregular Yo: -Zco Verbs

Verbs ending in -cer or -cir preceded by a vowel follow a predictable pattern: the yo form ends in -zco, while every other form is regular.

Why the -zco?

Before the vowel -o of the yo form, the soft c sound would otherwise become a hard k sound (as in conocer → conoco). Spanish protects the original soft sound by inserting -z-, giving conozco. Problem solved, sound preserved.

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This only applies when the -cer or -cir follows a vowel (cono-cer, pare-cer). If it follows a consonant (like vencer, ejercer), the change is different — those verbs use -zo without the c: venzo, ejerzo.

Conocer — the model verb

SubjectConjugation
yoconozco
túconoces
él / ella / ustedconoce
nosotros / nosotrasconocemos
ellos / ellas / ustedesconocen

Only the yo form is irregular. Everything else follows the regular -er pattern.

Yo conozco a tu hermana.

I know your sister.

¿Conoces esta canción?

Do you know this song?

Nosotros conocemos un buen restaurante.

We know a good restaurant.

Common -zco verbs

InfinitiveMeaningYo form
conocerto know (a person or place)conozco
parecerto seemparezco
crecerto growcrezco
nacerto be bornnazco
obedecerto obeyobedezco
ofrecerto offerofrezco
agradecerto thankagradezco
producirto produceproduzco
traducirto translatetraduzco
conducirto driveconduzco

Ofrezco mi ayuda siempre que puedo.

I offer my help whenever I can.

Yo traduzco documentos del inglés al español.

I translate documents from English to Spanish.

Conduzco con mucho cuidado en la lluvia.

I drive very carefully in the rain.

Producir — a full example

SubjectConjugation
yoproduzco
túproduces
él / ella / ustedproduce
nosotros / nosotrasproducimos
ellos / ellas / ustedesproducen

Again, only the yo form shows the irregularity. The rest follows the regular -ir pattern.

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Conocer means "to know (a person or place)," while saber means "to know (a fact or how to do something)." See the other irregular yo forms page for more on saber.

Common mistakes

❌ Yo conoco a tu hermana.

Wrong: the yo form needs -zco, not -co.

✅ Yo conozco a tu hermana.

Correct: conozco preserves the soft c sound.

❌ Yo conduco muy bien.

Wrong: -cir verbs also follow the -zco pattern in yo.

✅ Yo conduzco muy bien.

Correct: conduzco, not conduco.

❌ Yo conozco hablar español.

Wrong: conocer is for people and places, not skills.

✅ Yo sé hablar español.

Correct: use saber for knowing how to do something.

❌ Ella parezce simpática.

Wrong: the -zco change only happens in the yo form.

✅ Ella parece simpática.

Correct: all non-yo forms keep the regular -c- spelling.

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