A verbal periphrase is a fixed combination of an auxiliary verb, often with a preposition or that, and a non-finite form of the verb, such as the infinitive, gerund, or participle. It functions as a single verbal nucleus and conveys tense, aspect, or mood. It is distinguished from two verbs in sequence because it forms a single unit of meaning.

Periphrases are formed with a conjugated auxiliary verb and a main verb in the infinitive, gerund, or participle. The auxiliary provides tense and person. The main verb provides the lexical meaning of the action.

Verbal periphrases with the infinitive typically express near future, obligation, necessity, possibility, or intention. The infinitive remains unchanged and may take complements as a normal verb.

Periphrases with the gerund usually express progressive or durative aspect. In Spanish, the gerund indicates an action in development, not a time by itself.

Periphrases with the participle typically express result, resulting state, or perfective aspect. The participle agrees in gender and number if it functions as an adjective, but in periphrase it is usually invariable.

The aspect in periphrases indicates whether the action is presented as finished, in progress, or habitual. In Spanish, 'estar + gerund' focuses on development, and 'haber + participle' focuses on culmination.

Modality in periphrases expresses values such as obligation, possibility, intention, or probability. The periphrase is chosen according to the nuance you want to communicate, not only the content of the action.

"Tener que + infinitive" is personal obligation and "hay que + infinitive" is impersonal obligation. "Deber + infinitive" expresses obligation with often a softened or normative nuance.

"Ir a + infinitive" is used for near future or planned actions and competes with the simple future depending on context. In conversation, it is usually more natural for imminent decisions and actions.

"Seguir + gerund" expresses that an action continues and "llevar + gerund" expresses how long an action has been ongoing. Both emphasize persistence, but "llevar" incorporates a temporal measure.

"Tener + participio" typically expresses that a task is completed and available as a result, often with a complement. "Dar por + participio" communicates that the speaker considers a matter closed.

In periphrases, the main agreement is between the auxiliary and the subject in person and number. The participle only agrees in gender and number if it functions as an adjective or with passive constructions, not in "haber + participle".