Verb conjugation are rules for changing a verb to represent several qualities.
In Spanish some qualities are represented in almost every verb form. These primary qualities include person, number, tense/aspect and mood. Some verb forms incorporate one or more auxiliary or modal verbs to indicate additional quailities such as explicit duration, relevant anteriority, ability, permission, obligation and prohibition. The sets of primary and secondary qualities represented by individual verb forms in Spanish is different from the sets in English.
Modern Spanish verbs have approximately 48 distinct simple forms, which can be classified as finite verb forms and non-finite verb forms.
Finite verb forms
- Indicative Mood: these forms declare (or "indicate") what is or is not happening, did or did not happen, or will or will not happen.
- Subjunctive mood: these forms have several uses
- Imperative: 2 (or 3) positive forms for 2nd-person familiar. These forms are used when commanding someone to do or not to do something. All negative imperatives and all other positive imperatives are identical to present subjunctive forms.
Non-finite verb forms
These forms do not indicate person, number, tense, aspect or mood. By themselves the non-finite forms of a verb function as other parts of speech.
- Infinitive: The "dictionary" form of the verb. When used independently it always functions as a noun.
- Participle (or Past Participle): When used independently it always functions as an adjective or as a noun. When it is used as a noun, it has a different meaning from the infinitive. It also is used together with simple forms of the verb haber to form compound (or "perfect") tenses, and it also is used together with simple forms of the verb ser to form the true passive tenses.
- Gerund (or Present Participle): When used independently it always functions as an adverb. It also is used together with simple forms of the verb estar to form progressive (or continuous) tenses.