intervenir

to interveneirregular-ir verb

Where it breaks the pattern

intervenir follows venir: irregular first-person form
intervenir follows venir: e → ie when the stem is stressed
intervenir follows venir: irregular preterite stem; the 1s and 3s endings are unstressed, so they carry no written accent
intervenir follows venir: irregular future stem; the endings themselves are regular
intervenir follows venir: conditional shares the irregular future stem
intervenir follows venir: present subjunctive is built from the irregular yo form
intervenir follows venir: imperfect subjunctive is built from the third-person preterite stem
e → i outside the present, where the stem is unstressed

Indicativo: intervenir conjugation

	Presente	Pretérito	Imperfecto	Futuro	Condicional
yo	intervengo	intervine	intervenía	intervendré	intervendría
tú	intervienes	interviniste	intervenías	intervendrás	intervendrías
él / ella / Ud.	interviene	intervino	intervenía	intervendrá	intervendría
nosotros	intervenimos	intervinimos	interveníamos	intervendremos	intervendríamos
vosotros	intervenís	intervinisteis	interveníais	intervendréis	intervendríais
ellos / Uds.	intervienen	intervinieron	intervenían	intervendrán	intervendrían

Participio: intervenido · Gerundio: interviniendo

irregular form

Real sentences with the conjugated form highlighted, from Tatoeba, licensed under CC BY 2.0 FR.

Tom intervino en la disputa de sus colegas.
Tom intervened in his coworkers' disagreement.
Tal vez los ancianos de la villa intervengan para reconciliarlos.
Maybe the village elders will intervene to reconcile them.
El árbitro de hockey intervino para parar la pelea.
The hockey referee intervened to stop the fight.

These verbs are venir with a prefix, and they inherit its irregular forms.