what is it?
A group of common verbs is regular in the present except in the yo form, which takes an irregular ending. Many add a -go (as in hago, pongo, tengo), and verbs ending in -cer or -cir add a -zco (as in conozco). All the other persons follow the normal present pattern.
when to use it
Use the irregular ending only in the yo form: hago, salgo, conozco.
The -go group includes hacer, poner, salir, tener, venir, decir, oír, traer.
Verbs in -cer / -cir after a vowel take -zco: conocer → conozco.
Compounds keep the same irregular yo form as the base verb: mantener → mantengo.
formation
Take the verb, build the special yo form, and leave every other person as normal.
| verb | yo form | meaning |
|---|---|---|
| hacer | hago | I do / make |
| poner | pongo | I put |
| salir | salgo | I go out |
| tener | tengo | I have |
| venir | vengo | I come |
| decir | digo | I say |
| oír | oigo | I hear |
| traer | traigo | I bring |
| conocer | conozco | I know |
| conducir | conduzco | I drive |
| mantener | mantengo | I keep |
Compare the two persons: hago but haces; tengo but tienes. The irregular part lives only in yo.
examples in context
common pitfalls
Do not make the yo form regular. It is hago, pongo, salgo, not haco, pono, salo.
Keep the full -zco in -cer / -cir verbs: conozco, not conoco or conozo.
Compounds keep the irregular form too: mantengo and propongo, not mantieno or propono.
Do not spread the yo form to other persons. Say tú dices and él pone, not tú digas or él pongue.