Common Irregular Verbs - The "(C-ZC)" Change

Look at the verb conjugation table for conocer(to know):

conocer	to know
yo conozco	nosotros conocemos
tú conoces	vosotros conocéis
él, ella, Ud. conoce	ellos, ellas, Uds. conocen

The one thing you'll notice if you are paying attention to the conjugation pattern is that the yo form has a slight spelling change: the "c" changed to a "zc". Other than this irregularity in the yo form, the rest of the conjugation follows a regular pattern.

Other verbs that pattern like conocer are permanecer(to remain), pertenecer(to belong to), agradecer(to appreciate, to thank), and merecer(to deserve). Basically, any verb infinitive ending in -cer (with the exception of nacer(to be born) and hacer(to make, to do) are going to exhibit this irregularity.

Verbs that end in -cir like conducir(to drive) and producir(to produce) share this irregularity in the yo form as well. Look at the verb traducir:

traducir	to translate
yo traduzco	nosotros traducimos
tú traduces	vosotros traducís
él, ella, Ud. traduce	ellos, ellas, Uds. traducen

As you will see for the rest of the verb after the yo form, the conjugation pattern is regular in its entirety.