Celery, (Apium graveolens), herbaceous plant of the parsley family (Apiaceae). Celery is usually eaten cooked as a vegetable or as a delicate flavouring in a variety of stocks, casseroles, and soups. In the United States raw celery is served by itself or with spreads or dips as an appetizer and in salads. The tiny seedlike fruits, known as celery seed, resemble the plant itself in taste and aroma and are used as a seasoning, particularly in soups and pickles.