Gerundios irregulares: pidiendo, durmiendo, leyendo

Once you have the regular gerundio (hablando, comiendo, viviendo) firmly in place, you are ready for the irregulars. The good news is that there are only two patterns, both completely predictable, both shared with the preterite, and both affecting only a defined set of verbs. Once you have learned the patterns, you will never need to look up a gerund again.

The two patterns at a glance

These are the only two patterns. Once you can recognise which pattern a verb falls under (and many verbs fall under neither, staying perfectly regular), the form follows automatically.

Pattern 1: -ir verbs with stem change

The single biggest source of irregular gerunds in Spanish. The rule: any -ir verb whose stem changes in the present indicative (e → ie or o → ue) or that has a "hidden" e → i change shows a stem change in the gerundio too — specifically, e → i or o → u. This is the same change that appears in the 3rd-person preterite (pidió, durmió).

The change happens because in -ir verbs, an unstressed e in the stem cannot survive in front of certain endings without raising one notch (e → i); the same applies to unstressed o → u. (No need to memorise the phonological reasoning; just connect this gerund to the preterite stem and you will remember it.)

-ir verbs with e → i

Two clarifications about this list:

• Decir and venir are normally taught as "irregular" verbs in the present, but their gerundio (diciendo, viniendo) is just the regular -ir e → i pattern.
• Reír drops one -i- in the spelling: not *reiendo with two i*s, but *riendo with one. Same goes for sonriendo.

-ir verbs with o → u

There are only two verbs in everyday Spanish that show this pattern, plus their compounds.

That is the whole list. Two verbs to memorise. (Poder technically follows the same o → u pattern, giving pudiendo — but poder hardly ever appears in progressive constructions, so you rarely meet the form in everyday Spanish.)

Pattern 2: unstressed -i- between vowels becomes -y-

This is a spelling-driven pattern that affects -er and -ir verbs whose stem ends in a vowel — leer, oír, traer, caer, huir, construir. In Spanish spelling, an unstressed i between two other vowels cannot stay as i; it has to be written y. The regular ending -iendo gets caught in this rule: when added to a vowel-final stem, the -i- of -iendo becomes -y-, giving -yendo.

The special case of ir

Ir is the most irregular verb in Spanish, but its gerund — yendo — actually follows Pattern 2 perfectly. The "stem" of ir (after dropping -ir) is just an empty slot, and adding -iendo and applying the i → y rule gives yendo. So the form is logical; what is unusual is that yendo appears in very limited contexts (you almost never say *estoy yendo for I'm going — Spanish uses simple voy instead).

That sentence is the kind of context where yendo really does fit naturally — with iba (imperfect of ir) as the auxiliary expressing a process in motion. As a bald estoy yendo, it is grammatical but heavily marked.

Verbs that look like they should be irregular but are not

Several verbs feel like they ought to take an irregular gerund but stay regular. Watch out for these false alarms.

• -ar and -er stem-changers stay regular: pensar → pensando, volver → volviendo, jugar → jugando. The stem change in the present is stress-driven, and in the gerund the stress is on the ending, so no change. (See the formation page for the full rule.)
• Tener and poner are regular: teniendo, poniendo. These are -er verbs, so the e → i pattern from -ir does not apply.
• Hacer, querer, saber are all regular: haciendo, queriendo, sabiendo. Again, all -er, all regular gerunds.
• Estar, ser, haber: estando, siendo, habiendo. Regular. (You will see siendo and habiendo in absolute constructions: Siendo así, no voy; Habiendo terminado, salieron.)

How English speakers go wrong with these forms

The patterns are predictable, so most errors come from forgetting to apply them — producing a regular gerund where an irregular one is required.

Forgetting the -ir stem change

The most common error. Learners produce *pediendo, *serviendo, *moriendo, *sentiendo — regular-looking gerunds for -ir verbs that should stem-change. They have learned the regular pattern first and over-generalise it.

Writing -iendo instead of -yendo

Spelling slip. The pattern i → y between vowels is hard to remember in the moment because the pronunciation does not change much.

Over-applying -ando to all -ar verbs without thinking

Not actually an irregularity, but worth flagging: poder is -er, so its gerund is pudiendo, not *podando (which would be the gerund of podar, "to prune"). Always check the conjugation class.

Common Mistakes

Key takeaways

• There are only two patterns of irregular gerundio in Spanish: -ir stem change (e → i, o → u) and unstressed -i- between vowels → -y-.
• The -ir stem-change pattern mirrors the 3rd-person preterite stem: if you know pidió, you know pidiendo.
• The o → u pattern affects only dormir and morir (plus compounds) in everyday Spanish.
• The i → y pattern affects -er and -ir verbs whose stem ends in a vowel: leer, oír, huir, construir, ir, and so on.
• Stem-changers in -ar and -er are regular in the gerund. The change is restricted to -ir verbs.