Mirepoix (cuisine)
Similar flavour bases include the Italian "soffritto", the Spanish "sofrito", "refogado/sufrito" (braised onions, garlic and tomato) from Portuguese-speaking nations, the German "suppengrün" (leeks, carrots and celeriac), the Polish "włoszczyzna" (leeks, carrots, celery root and parsley root), the US Cajun / Creole holy trinity (onions, celery and bell peppers), and possibly the French "duxelles" (mushrooms and often onion or shallot and herbs, reduced to a paste).
Celery
Celery is eaten around the world as a vegetable. In North America the crisp petiole (leaf stalk) is used. In Europe the hypocotyl is used as a root vegetable. The leaves are strongly flavored and are used less often, either as a flavoring in soups and stews or as a dried herb. Celery, onions, and bell peppers are the "holy trinity" of Louisiana Creole and Cajun cuisine. Celery, onions, and carrots make up the French mirepoix, often used as a base for sauces and soups. Celery is a staple in many soups, such as chicken noodle soup.