The Liliaceae, or the lily family, are a family of monocotyledons in the order Liliales. Plants in this family have linear leaves, mostly with parallel veins but with several having net venation (e.g., Cardiocrinum, Clintonia, Medeola, Prosartes, Scoliopus, Tricyrtis), and flower arranged in threes. Several have bulbs, while others have rhizomes. Shade-dwelling genera usually have broad, net-veined leaves, fleshy fruits with animal-dispersed seeds, rhizomes, and small, inconspicuous flowers; genera native to sunny habitats usually have narrow, parallel-veined leaves, capsular fruits with wind-dispersed seeds, bulbs, and large, visually conspicuous flowers.
Many plants in the Liliaceae are important ornamental plants, widely grown for their attractive flowers. Many species are poisonous if eaten and may cause serious complications, such as renal failure in household pets, especially cats.
The lily family was formerly a paraphyletic "catch-all" group of petaloid monocots that did not fit into other families. It included a great number of genera now included in other families and in some cases in other orders, including Agavaceae, Alliaceae, Amaryllidaceae, Asparagaceae, Asphodelaceae, Hyacinthaceae, Melanthiaceae, Nartheciaceae, Ruscaceae, Smilacaceae, Tecophilaeaceae, Themidaceae, Tofieldiaceae, and Uvulariaceae, and members of the monocot orders Asparagales, Dioscoreales, and Alismatales. Smilacaceae appears to be the family most closely related to Liliaceae in its modern restricted sense.
Lilium (members of which are true lilies) is a genus of herbaceous flowering plants growing from bulbs, all with large prominent flowers. Lilies are a group of flowering plants which are important in culture and literature in much of the world. Most species are native to the temperate northern hemisphere, though their range extends into the northern subtropics. Many other plants have "lily" in their common name but are not related to true lilies.