ellos corrían

they ran, they were running

→ correr
corr run + ían 3rd person plural imperfect (indicative or subjunctive)
verb · third plural · imperfect indicative Rare #45,616
they ran, they were running
SP: Los niños corrían por el parque.
EN: The children were running through the park.
Conjugation of correr
Indicative imperfect
SingularPlural
First corría
Third corría corrían
Subjunctive imperfect
SingularPlural
First corría
Third corría corrían

Especialmente cuando corrían entre ellos.

Especially when they were running among themselves.

— Senna (2010)

Lágrimas corrían por sus mejillas.

Tears ran down her cheeks.

El grupo de payasos comenzó a tropezar mientras corrían.

The group of clowns began to stumble as they ran.

Recuerdo que todos corrían ese día..

I remember that everyone was running that day.

— Las flores de la guerra (2011)