Understanding Spanish verb structure: A guide for learners

Spanish verbs carry a remarkable amount of information in a single word. Unlike English, where we often need helper words and pronouns to express who is doing something and when, Spanish packs all of this into the verb itself. This guide will help you understand how Spanish verbs are built and what each part tells you.

The two main parts of a Spanish verb

Every Spanish verb form consists of two essential components: the stem (or root) and the endings. The stem carries the core meaning of the verb, while the endings provide grammatical information about who is performing the action and when it happens.

Take the verb trabajar (to work). In the form trabajaba (I/he/she used to work / was working), we can identify trabaj- as the stem and -aba as the ending. The stem remains constant in regular verbs throughout all their forms, while the ending changes to express different meanings.

What the endings tell you

Spanish verb endings communicate four key pieces of information: person (who is doing the action), number (one person or several), tense (when the action occurs), and mood (whether the action is stated as fact, commanded, or hypothetical).

Consider the form escribimos from escribir (to write). The ending -imos tells us that the subject is nosotros (we), that there are multiple people involved, that the action is in the present, and that the speaker is stating this as a fact (indicative mood). All of this information comes from just four letters.

The three conjugation groups

Spanish verbs are organized into three conjugation groups based on the ending of their infinitive form. The first group includes verbs ending in -ar (like hablar, to speak). The second group contains verbs ending in -er (like beber, to drink). The third group comprises verbs ending in -ir (like vivir, to live).

The vowel in the infinitive ending (a, e, or i) is called the theme vowel, and it often appears in other forms of the verb as well. Knowing which conjugation group a verb belongs to helps you predict its forms, since verbs within the same group follow similar patterns.

Breaking down the ending

Linguists often divide verb endings into smaller segments to better understand their function. In many verb forms, we can identify three components within the ending: the theme vowel, a segment indicating tense and mood, and a segment indicating person and number.

For example, in comíamos (we used to eat / were eating), we can identify: com- (stem, meaning eat), -í- (theme vowel), -a- (imperfect tense marker), and -mos (first person plural marker). As a learner, you don't need to analyze every form this way, but understanding the system can help you see patterns.

Irregular verbs: When the stem changes

While regular verbs maintain the same stem throughout their conjugation, many common Spanish verbs have stems that change in certain forms. These changes can affect vowels, consonants, or both.

Vowel changes are common. The verb pensar (to think) changes its stem from pens- to piens- in stressed syllables, giving us pienso (I think) but pensamos (we think). Consonant changes also occur: conocer (to know) changes from conoc- to conozc- before the vowel o, producing conozco (I know).

Some verbs undergo dramatic stem changes, where the conjugated form looks quite different from the infinitive. The verb ir (to go) produces forms like voy (I go) and fui (I went), which share no obvious visual connection with the infinitive. These are called suppletive forms and must simply be memorized.

Non-finite forms: Infinitives, gerunds, and participles

Not all verb forms indicate person and number. Spanish has three non-finite forms that function differently from conjugated verbs: the infinitive (hablar, to speak), the gerund (hablando, speaking), and the past participle (hablado, spoken).

The infinitive is the form you find in dictionaries and consists of the stem plus -ar, -er, or -ir. The gerund is formed by adding -ando to first conjugation stems and -iendo to second and third conjugation stems. The past participle takes -ado for first conjugation verbs and -ido for second and third conjugation verbs.

Simple vs. compound tenses

Spanish verb forms can be either simple (consisting of one word) or compound (using two words). Simple forms like hablé (I spoke) express the complete meaning in a single word. Compound forms combine the auxiliary verb haber with a past participle, as in he hablado (I have spoken).

In compound tenses, the auxiliary verb haber carries the information about person, number, tense, and mood, while the past participle remains unchanged regardless of the subject. Whether you say he comido (I have eaten), has comido (you have eaten), or han comido (they have eaten), the participle comido stays the same.

The three moods

Spanish organizes its verb tenses under three moods. The indicative mood is used for statements of fact and includes tenses like the present (corro, I run), the preterite (corrí, I ran), and the future (correré, I will run).

The subjunctive mood expresses wishes, doubts, possibilities, and emotions. It appears after certain triggers or inductors, as in Espero que corras (I hope that you run) or Dudaba que corriera (I doubted that he/she would run).

The imperative mood is used for commands and requests, as in ¡Corre! (Run!). It has limited forms, primarily for tú and vosotros.

Practical tips for learners

Understanding verb structure helps you learn more efficiently. When you encounter a new verb, identify its conjugation group from the infinitive ending. For regular verbs, knowing the patterns for one verb in each group means you can conjugate hundreds of others.

Pay attention to irregular patterns. Many stem changes follow predictable rules (like e becoming ie in stressed syllables), and similar verbs often share the same irregularity. The verb cerrar (to close) changes like pensar because they share the same pattern of stem-change.

Finally, remember that verb endings encode agreement with the subject. This means Spanish speakers often omit subject pronouns because the verb ending already tells you who is performing the action. When you say estudiamos, the -amos ending makes it clear you mean we study, so adding nosotros is usually unnecessary.