Spanish irregular verbs


are a complex area of Spanish grammar, with many combinations of tenses, aspects and moods. Although conjugation rules are relatively straightforward, a large number of verbs are irregular. Among these, some fall into more-or-less defined deviant patterns, whereas others are uniquely irregular. This article summarizes the common irregular patterns.
As in all Romance languages, many irregularities in Spanish verbs can be retraced to Latin grammar.

Orthographic changes

Due to the rules of Spanish orthography, some predictable changes are needed to keep the same consonant sound before a or o and e or i, but these are not usually considered irregularities. The following examples use the first person plural of the present subjunctive:
Other predictable changes involve stress marks, i—y alternations and i-dropping, some of which are sometimes considered as irregularities. The examples are several forms of otherwise regular preterites:
There are two kinds of changes that can affect stem vowels of some Spanish verbs: diphthongization and [|vowel raising]. Both changes affect -e- or -o- in the last syllable of a verb stem. Diphthongization changes -e- to -ie-, and -o- to -ue-. Vowel raising changes the mid vowels -e- and -o- to the corresponding high vowels: -i- and -u- respectively. Some verbs, in their various forms, can exhibit both kinds of changes .

Diphthongization

Some verbs with -e- or -o- in their stem are inherently diphthongizing, whereas others are not: their identities must be learned individually.
In a diphthongizing verb, the change turns -e- into -ie- and -o- into -ue- when the syllable in question is stressed, which in effect happens only in the singular persons and third-person plural of the present indicative and present subjunctive, and in the imperative. Note that the dictionary form always has the vowel, not the diphthong, because, in the infinitive form, the stress is on the ending, not the stem. Exceptionally, the -u- of jugar and the -i- of adquirir also are subject to diphthongization.
In word-initial position, *ie- is written ye- and *ue- is written hue- . Also, the -ue- diphthong is written -üe- after g, with the diaeresis to indicate that the letter is not silent .
The following examples show that all three conjugations include some diphthongizing verbs :

Present indicative

Present subjunctive

In Central America pensés, contés, etc. are used, but Spanish Royal Academy prescribes , , etc., according to Rioplatense Spanish.

Imperative

Note that sentir and dormir also undergo vowel raising. Additional diphthongizing verbs include acordar, divertir, doler, empezar, encontrar, entender, llover, morir, mostrar, mover, poder, probar, querer , recordar, sentar, tener, venir, volar, and volver.
Many verbs with -e- or -o- in the root do not alternate. Common non-diphthongizing verbs include acercar, beber, comer, comprar, conocer, correr, creer, deber, dejar, entrar, esperar, lamentar, llegar, llevar, meter, parecer, poner, prometer, quedar, regresar, responder, suceder, temer, and tomar.
Less frequent verbs of this kind are often a source of mistakes for children learning to speak, and also for some adults:
Vowel raising appears only in verbs of the third conjugation, and in this group it affects dormir, morir, podrir and nearly all verbs which have -e- as their last stem vowel ; exceptions include cernir, discernir and concernir.

Affected forms

The forms that exhibit the change can be described negatively as those in which the stem vowel is not diphthongized and the ending does not contain stressed i or the -ir- sequence. In other words, vowel raising affects the forms whose endings do not contain an i which is not part of a diphthong, taking into account that diphthongizing overrides vowel raising.
In effect, for diphthongizing verbs, the vowel-raising forms are:
For non-diphthongizing verbs it affects these same forms, plus:
The forms which do not undergo either diphthongizing or vowel raising are:
Verbs which are diphthongizing and vowel-raising include:
The diphthongizing -er verb poder exceptionally undergoes vowel rising in the gerund, but the first- and second-person plural of the present subjunctive are regular.
Non-diphthongizing vowel-rising verbs include:
The vowel-raising verb erguir is usually diphthongizing, not-diphthongizing forms are however valid but rare .

Diphthongs and hiatuses (diptongos y hiatos)

''Cambio'' vs. ''envío''

s in the infinitive may be preserved throughout the conjugation or broken in the forms which are stressed on the stem, depending on whether the i or u in contact with a/e/o take the stress or not. The stressed vowel is marked bold in the examples: cambiar > cambio, but enviar > envío. The Real Academia Española does not consider either behaviour as irregular, but illustrates each with six "regular" models, one for each possible diphthong in the infinitive: anunciar, averiguar, bailar, causar, peinar and adeudar for diphthong-keeping verbs and enviar, actuar, aislar, aunar, descafeinar and rehusar for diphthong-breaking ones. Remember that the presence of a silent h does not break a diphthong, so a written accent is needed anyway in rehúso.
All verbs ending in -guar are diphthong-keeping, as well as saciar, desairar, restaurar and reinar. Note that two diphthongs are kept in desahuciar > desahucio, which thus follows both the anunciar and causar models.
Diphthong-breaking verbs include ahincar, aislar, aunar, aullar, maullar, aupar, aliar, vaciar, contrariar, evaluar, habituar, reunir. The verbs criar, fiar, guiar, liar and piar are also diphthong-breaking, but when the stress falls on the endings the resulting forms are generally considered as monosyllables and thus written without accent: crie, fie, guiais, lieis.... In spite of that, the regular accentuation rules can also be used if they are pronounced as bisyllabic: crié, guiáis....
For the verbs licuar and adecuar both options are valid: adecuo or adecúo.
Note that the ui diphthong in cuidar is kept throughout the conjugation despite the fact of the i getting the stress in forms such as cuido.

Verbs ending in ''-uir'' and ''-oír''

All verbs ending in -uir add a medial -y- before all endings not starting with i: construyo, construyes, construya... Taking into account that these verbs also undergo the change of unstressed intervocalic i to y, they have many forms containing y.
This also applies to the forms of oír and desoír that do not undergo the -ig- change: oyes, oye, oyen
Again, note that some regular forms of fluir, fruir and huir are written without stress mark if considered monosyllabic, but may bear it if pronounced as bisyllabic: vosotros huis or huís, yo hui or huí.
Note that logically argüir loses the diaeresis before y: arguyo, arguyó...

Other common irregular patterns

Endings starting with ''o/a'' in ''er/ir'' verbs

In er and ir verbs, the first person singular of the present indicative and the whole present subjunctive are the only forms whose endings start with o/a instead of e/i. These two different phonetic environments made Latin forms evolve differently in many verbs, leading to irregularities. Note that:
Before o and a, the so-called G-verbs add a medial -g- after l and n, add -ig- when the root ends in a vowel, or substitute -g- for -c-. Note that this change overrides diphthongization but combines with vowel-raising. Many of these verbs are also irregular in other ways. For example:

ZC-verbs

This group of verbs—which originated in the Latin inchoative verbs but now includes other verbs as well— substitute -zc- for stem-final -c- before o and a. The group includes nearly all verbs ending in -acer, -ecer, -ocer, and -ucir. For example:
Yacer may alternatively be conjugated with -zc-, -g- or a compromise -zg-.

Irregular forms in the future, conditional and imperative

Some -er and -ir verbs also change their stem in the future and conditional tenses. This involves:
Many of these verbs also have shortened tú imperative forms: tener → ten, contener → contén, poner → pon, disponer → dispón, venir → ven, salir → sal, hacer → haz, decir → di. However, all verbs derived from decir are regular in this form: bendice, maldice, desdícete, predice, contradice.

Anomalous stems in the preterite and derived tenses

Some verbs have a somewhat different stem in the preterite. These stems are very old and often are found in Latin as well. The same irregular stem is also found in the imperfect subjunctive and the future subjunctive. This stems are anomalous also because:
Examples:

Irregular past participles

A number of verbs have irregular past participles, sometimes called "strong" because the change is in the root, rather than an ending. This includes verbs which are irregular in many other ways, as poner and decir, but for some other verbs this is their only irregularity, while some very irregular verbs have regular past participles. Examples:
Most of these verbs have derivatives with the same irregularity. For example, alongside volver → vuelto and poner → puesto there are devolver → devuelto and componer → compuesto; alongside decir → dicho there is predecir → predicho. Similarly previsto, rehecho, descubierto, supuesto, etc. Solver is obsolete, but its derivatives absolver and resolver are in common use. The participle of describir is descrito in some regions, but descripto in others.
There are three verbs that have both a regular and an irregular past participle. Both forms may be used when conjugating the compound tenses and the passive voice with the auxiliary verbs haber and ser, but the irregular form is generally the only one used as an adjective:
A number of other "strong" past participles, such as pinto, ducho, electo, and a number of others, are obsolete for general use, but are occasionally used in Spain among educated, style-conscious writers, or in linguistic archaisms such as proverbs.

Others

The verbs ser and ir both exhibit irregularities in the present, imperfect and preterite forms. Together with ver and prever, they are the only four verbs with irregular imperfect indicative. Their tú imperative forms are sé, ve and prevé. Their vos imperative forms are sé, andá, ve and prevé.
Remember that whenever the preterite is irregular, the imperfect subjunctive and the dated future subjunctive share the same irregularity; indeed, these tenses may always be correctly formed by substituting the appropriate endings for the -ron ending of the third person plural preterite: fueron > fuera/fuese,...; fuere....
The verbs dar and estar both exhibit irregularities in the present indicative and present subjunctive because their stems cannot be stressed. The form dé is so written to distinguish it from the preposition de. Both verbs are also irregular in the preterite and derived tenses: dar follows the pattern of regular -er/-ir verbs, while estar has an [|anomalous preterite stem] and follows the corresponding common pattern: