lamentar
/lamenˈtaɾ/ · B1 · verb
to lament, to regret
😢 From Latin lamentari, to wail; same root as English lament
Spanish lamentar and English lament both come from Latin lamentum, a wail or cry of grief. The meaning is the same as in English. Lo lamento means I'm sorry about it, and lamentar la muerte de alguien means to mourn someone's death.