Verbos en -cer/-cir: yo -zco (conocer, parecer, conducir)

A second family of irregular yo-forms covers verbs that end in vowel + -cer or vowel + -cir. Their only present-indicative quirk is that the yo form takes a -zco ending: conozco, parezco, agradezco, ofrezco, traduzco, conduzco, produzco. Every other person in the paradigm uses the standard -er or -ir endings, so once you secure the yo you get the rest for free.

The class is large and productive — almost any new -cer verb a learner meets in modern Spanish (establecer, reconocer, enriquecer, fortalecer) follows the same pattern. The trick is recognising that the vowel before -cer / -cir is what triggers the rule. Verbs where a consonant precedes the -cer — like vencer ("to defeat") — behave entirely differently, taking only a c → z spelling change (venzo) and no extra -c-. A handful of irregular look-alikes (notably cocer, "to cook") also fall outside the -zco class for historical reasons; we cover them at the end.

The rule in one line

If the infinitive ends in vowel + -cer or vowel + -cir, the yo form is stem + -zco. The other persons are regular.

Full paradigm — conocer

Here is the entire present indicative of conocer, showing how only the yo form is irregular.

Notice the personal a in the second example: when the direct object of conocer is a specific human, Spanish inserts the preposition a. Conocer a alguien = to know someone; conocer un lugar = to know a place. Get this distinction wrong and the sentence shifts in meaning.

Full paradigm — conducir

The -ducir subfamily works exactly the same way, just with -ir endings.

Parecer — "to seem"

Parecer is one of the most useful verbs in conversational Spanish, because it powers a whole opinion-asking construction.

The construction me/te/le/nos/os/les parece + adjective is the Spanish equivalent of English I think it's... or I find it.... It is heard constantly in opinion-sharing: me parece bien, me parece mal, me parece fatal, me parece interesante.

Why -zco and not just -co or -zo?

A historical aside that makes the pattern stick. In Latin, verbs of this class used a -sco infix (an inchoative marker that originally signalled beginning to do something: crēscō = "I am growing"). Over time, Spanish reanalysed that -sc- into a -zc- — pronounced /θk/ in Peninsular Spanish, /sk/ in Latin America. The z before c is not just a spelling oddity; it preserves a distinct sound that the Latin ancestor already had.

This is why vowel + -cer / -cir verbs take -zco but consonant + -cer verbs (like vencer, "to defeat") do not. Vencer did not have the -sc- infix in Latin, so its yo form is just venzo — a simple c → z spelling change in front of o, with no extra c. Compare:

• conocer (inherited the inchoative -sc- from Latin cognoscere) → conozco ✓
• vencer (consonant before -cer, no inchoative -sc-) → venzo, not ✱venzco
• cocer (from Latin coquere, no inchoative -sc-; takes an o → ue stem change instead) → cuezo, not ✱cuezco

The fastest visual diagnostic still works for the vast majority of cases: vowel + -cer / -cir = expect -zco. The classic exception is cocer — looks like it should join the family, but doesn't, because its Latin ancestor never had the inchoative suffix to begin with.

Peninsular pronunciation — the /θ/ sound

This is where European Spanish makes itself heard. The letter z in any position, and the letter c before e or i, is pronounced /θ/ in Spain — the same sound as the th in English think. So conozco is pronounced roughly /ko.ˈnoθ.ko/ (ko-NOTH-ko), and parezco is /pa.ˈɾeθ.ko/ (pa-RETH-ko).

In most of Latin America (and the Canary Islands, and parts of Andalusia), this th sound has merged with /s/ — a phenomenon called seseo. There, conozco sounds like ko-NOS-ko. Both pronunciations are correct in their own regions; the Spain-wide standard is the th-sound.

Conocer vs saber — two ways to "know"

Spanish splits English know into two verbs, and the conozco/conocer family covers only one side of it.

• Conocer = to be acquainted with — a person, a place, a work of art. Implies first-hand familiarity.
• Saber = to know a fact, a piece of information, or how to do something.

Note that saber is not a yo-zco verb — its yo form is the irregular monosyllable sé. See the other irregular yo family page for the cousins.

Common mistakes

Key takeaways

• Verbs in vowel + -cer / -cir take -zco in the yo form: conozco, parezco, agradezco, ofrezco, traduzco, conduzco.
• The rest of the paradigm uses the standard -er / -ir endings — only yo is irregular.
• Verbs in consonant + -cer do not join the family. Vencer → venzo; cocer → cuezo.
• The -zco form carries the peninsular /θ/ sound, which propagates throughout this class and is central to the Spain-Spanish accent.
• Conocer and saber both translate as know, but cover different territory: people/places (conocer) vs facts/skills (saber).
• This yo stem feeds the entire present subjunctive: conozca, conozcas, conozca, conozcamos, conozcáis, conozcan.

For the parallel pattern in verbs that insert -g- in the yo form, see the yo-go family.