Two small but distinctive families of verbs share the last three letters of the infinitive — -uir — and yet behave completely differently. Verbs ending in -guir (with a g before the u) are the seguir, conseguir, distinguir family: their silent u disappears the moment the ending starts with -o- or -a-. Verbs ending in -uir with no preceding g (such as construir, huir, incluir, contribuir) do the opposite: they insert a y before personal endings that start with -o-, -e-, -a-. Both patterns produce a yo form that surprises learners on first contact — sigo, distingo, construyo, huyo — but each is regular once you see the underlying logic.
Pattern 1: -guir verbs drop the silent u
In Spanish, the letter combination gu before e or i is a single sound: a hard /g/ followed by the vowel, with the u silent. Guerra is /ge-rra/, guitarra is /gi-ta-rra/. The u is there only to tell the reader "the g is hard — don't pronounce it like gente."
The verb seguir uses this trick. The stem is segu-, pronounced /seg-/ with a silent u. As long as the next vowel is -e- or -i-, the u has a job: it keeps the g hard. But when the ending is -o or -a, the u is no longer needed — g before o is already hard — so Spanish drops the silent u to avoid an unnecessary letter.
To complicate things just slightly, seguir is also an e→i stem-changer, so the yo form combines two changes: e→i in the stem and the dropped u. The result is sigo.
| Subject | seguir | distinguir |
|---|---|---|
| yo | sigo | distingo |
| tú | sigues | distingues |
| él / ella / usted | sigue | distingue |
| nosotros / nosotras | seguimos | distinguimos |
| vosotros / vosotras | seguís | distinguís |
| ellos / ellas / ustedes | siguen | distinguen |
Notice the difference between the two verbs. Seguir has the e→i stem change and drops the u. Distinguir has no stem change — its stem vowel is -i-, not -e- — so the only thing that happens in the yo form is the dropped u: distingo. The vosotros form distinguís keeps the u because the ending begins with -í-, where the u is doing its silent job.
Sigo el camino que me has dicho.
I'm following the route you told me.
Yo distingo perfectamente entre el catalán y el gallego.
I can easily tell Catalan and Galician apart.
¿Seguís en Madrid o ya os habéis mudado?
Are you guys still in Madrid, or have you moved already?
The full -guir family
The common -guir verbs in everyday peninsular Spanish:
| Verb | Meaning | Stem change | Yo form |
|---|---|---|---|
| seguir | to follow, to continue | e→i | sigo |
| conseguir | to get, to manage to | e→i | consigo |
| perseguir | to chase, to pursue | e→i | persigo |
| proseguir | to continue (formal) | e→i | prosigo |
| distinguir | to distinguish, to tell apart | (none) | distingo |
| extinguir | to extinguish | (none) | extingo |
The first four are built on seguir and inherit its e→i stem change. The last two have an -i- stem to begin with, so the only thing that happens is the silent u dropping out in yo.
Consigo trabajo en cualquier sitio donde quieran un traductor.
I find work anywhere they need a translator.
No distingo bien los colores azul y verde con poca luz.
I can't tell blue from green well in low light.
Pattern 2: -uir verbs insert a -y-
Verbs ending in -uir without a preceding g — construir, destruir, huir, incluir, influir, contribuir, sustituir, atribuir — behave in a very different way. The infinitive ends with a stressed -uí (the u is a vowel here, not silent), and when a personal ending starting with -o-, -e-, -a- is added, Spanish inserts a glide consonant -y- between the u and the ending. So construir → construyo, construyes, construye, construyen.
The reason is acoustic. Construo would force two strong vowels (u and o) into separate syllables, which Spanish finds awkward. Inserting a -y- turns the cluster into a smooth consonant-vowel boundary: /kon-stru-yo/ rather than /kon-stru-o/.
| Subject | construir | huir |
|---|---|---|
| yo | construyo | huyo |
| tú | construyes | huyes |
| él / ella / usted | construye | huye |
| nosotros / nosotras | construimos | huimos |
| vosotros / vosotras | construís | huis |
| ellos / ellas / ustedes | construyen | huyen |
Two details deserve attention.
First, the -y- appears in four forms, not just one. The full distribution is: yo, tú, él, ellos all get the -y-; nosotros and vosotros don't. This looks like a "boot" pattern (the same shape as a stem-changer), but it is not a stem change — it is a spelling adjustment driven by the ending. Where the ending starts with -o-, -e-, -a-, the -y- is inserted. Where it starts with -í- or -i- (the nosotros -imos and vosotros -ís), the -y- is not.
Second, watch the vosotros form of huir. Since the 2010 RAE spelling reform, the form is officially written huis without an accent — the ui sequence is treated as a single-syllable diphthong, making the word monosyllabic and therefore unaccented by rule. Older texts and many native speakers still write huís with an accent (the pre-2010 norm), and you will see both forms in print. Compare with construís: here the word is unmistakably two syllables (con-stru-ís), the stress falls on the final í, and the accent is required. The general principle: longer -uir verbs (construir, destruir, incluir) take the accent on -ís; the very short huir technically does not in current orthography, though the older huís is still widely accepted.
Construyen un puente nuevo sobre el río.
They're building a new bridge over the river.
Huyo del calor de Madrid en julio y agosto.
I escape Madrid's summer heat in July and August.
Te incluyo en el grupo de WhatsApp para que te enteres de los planes.
I'm adding you to the WhatsApp group so you find out about the plans.
The full -uir family
| Verb | Meaning | Yo form |
|---|---|---|
| construir | to build | construyo |
| destruir | to destroy | destruyo |
| incluir | to include | incluyo |
| excluir | to exclude | excluyo |
| concluir | to conclude, to wrap up | concluyo |
| contribuir | to contribute | contribuyo |
| distribuir | to distribute | distribuyo |
| atribuir | to attribute | atribuyo |
| influir | to influence | influyo |
| huir | to flee, to run away | huyo |
| sustituir | to substitute, to replace | sustituyo |
| disminuir | to reduce, to decrease | disminuyo |
A peninsular note: in everyday speech, several of these verbs are slightly formal. Contribuir, distribuir, sustituir belong to written and professional registers; in casual conversation Spaniards often reach for simpler alternatives (ayudar, repartir, cambiar). But huir, incluir, construir are perfectly conversational.
No incluyo el IVA, lo añado luego al precio total.
I don't include VAT — I add it later to the total.
Los precios disminuyen cada año durante las rebajas de enero.
Prices go down every year during the January sales.
The two patterns side by side
A clean comparison clarifies how the two families differ:
| -guir (seguir) | -uir (construir) | |
|---|---|---|
| Ending of infinitive | -guir (silent u) | -uir (vocalic u) |
| Change in yo | drop the u: sigo | insert -y-: construyo |
| Affected forms | only yo | yo, tú, él, ellos (the "boot") |
| Trigger | back vowel ending (-o, -a) | back vowel ending (-o, -e, -a) |
| Stem change? | often (e→i in seguir, etc.) | never |
The visual giveaway in the infinitive is whether there's a g before the u. G+u = silent u, dropping pattern. No g = vocalic u, -y- insertion pattern. Once you internalise this distinction, you'll never mix up sigo and construyo.
A peninsular dialogue using both patterns
—¿Sigues yendo al gimnasio que hay al lado del Retiro?
Are you still going to the gym next to the Retiro?
—Sí, pero ahora cambian las clases cada semana, así que voy menos.
Yes, but now the classes change every week, so I go less.
—Pues yo huyo del gimnasio en verano, hace demasiado calor.
Well, I avoid the gym in the summer — it's too hot.
—Vale, así nos vemos cuando construyan el polideportivo nuevo en septiembre.
OK, so we'll see each other when they finish building the new sports centre in September.
How English maps onto these patterns
English speakers find both patterns counter-intuitive for the same reason: in English, the spelling of a verb stem essentially never changes within the same tense. We write go and goes — and even that -es feels like an exception rather than a rule. Spanish, by contrast, modifies the spelling of the stem whenever the sound demands it.
The -guir pattern is easier to internalise because there's only one form to remember: the yo. The -uir pattern is harder because the -y- shows up in four out of six forms, and beginners often forget to insert it in tú, él, ellos (*construes, *construen are common errors).
The cleanest rule of thumb: if you can read the infinitive aloud and the u is silent, you'll drop it in yo. If the u is a real vowel you can pronounce, you'll need a -y- before any ending that starts with a non--i- vowel.
Common mistakes
❌ Yo segir hacia el sur.
Wrong — this isn't even a valid infinitive. The infinitive is *seguir* (with the silent u).
✅ Yo sigo hacia el sur.
Correct — *sigo*, with the e→i stem change and the silent u dropped.
❌ Yo construo una casa.
Wrong — missing the -y- that bridges the u and o.
✅ Yo construyo una casa.
Correct — the -y- is required before back-vowel endings in -uir verbs.
❌ Tú construes algo nuevo.
Wrong — the -y- is needed in tú, él, ellos as well, not just yo.
✅ Tú construyes algo nuevo.
Correct — the -y- appears in the whole boot: yo, tú, él, ellos.
❌ Nosotros construyimos un puente.
Wrong — nosotros and vosotros do not get the -y-, because the ending starts with -i-.
✅ Nosotros construimos un puente.
Correct — no -y- when the ending begins with -i-.
❌ Yo distinguo los acentos.
Wrong — leaving the silent u where it doesn't belong. Before -o the u has no job.
✅ Yo distingo los acentos.
Correct — drop the silent u in the yo form.
Key takeaways
- -guir verbs (seguir, conseguir, distinguir) drop the silent u in the yo form: sigo, consigo, distingo. Several of them (the seguir family) also undergo an e→i stem change.
- -uir verbs (construir, huir, incluir, contribuir) insert a -y- in the yo, tú, él, ellos forms: construyo, construyes, construye, construyen. The nosotros and vosotros forms keep the simple -u-.
- The two patterns are triggered by the same condition — an ending starting with -o-, -e-, -a- — but solve it in opposite ways: drop a u (because the hard g no longer needs protection) or insert a -y- (because the vocalic u needs a consonant bridge).
- The visual cue in the infinitive: g before the u signals the -guir family; no g signals the -uir family.
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