The lily family used to contain a lot of other monocotyledonous varieties that are now classified as families in their own right, including members of Asparagaceae and Amaryllidaceae.
Description
Herbacious bulbous (rarely rhizomous) plants having flowers of 6 tepals. They can sometimes look like a grassy shrub, and other times, they can form a longer stem. Bracts may or may not be present on the flower buds.
Seeds within the family can come in a range of shapes, but the usually dehiscent seed pods split in 3 to reveal them.
Dehiscent seed capsule opening to reveal round seeds of Lilium nepalense. Image source
Flowers, Fruits & Leaves
Tepals: 3 sepals and 3 petals that are generally the same colour and not easy to distinguish, called tepals.
Male: 6 stamina.
Female: 3-parted stigma on a single pistil, with a superior ovary.
Fruit: A capsule splits in 3 to release seeds.
Seeds: Usually built to catch the wind, sometimes with a wing, tails or hair.
Leaves: Alternate leaves are in a spiral, or they can be whorled. They are simple, usually with parallel, occasionally netted, venation.
Noteworthy Types
Lilium is the genus of true lilies. A popular lily is stargazer Lilium orientalis which has large, showy tepals.
The stargazer lily Lilium orientalis. Image source
Tiger lily is a term that could point to several Lilium spp. that have recurved (bent backwards) tepals that are (usually) orange with black speckles.
A tiger lily, Lilium lancifolium. Image source
Easter lily Lilium longiflorum shows the flower in an outward-facing trumpet form.
An easter lily Lilium longiflorum with its signature trumpet shape. Image source
Along with true lilies, tulips Tulipa spp. are one of the most significant groups within the family, at least economically speaking.
Tulipa sp. Image source
Conclusion
There are a few look-alike families with members that look very similar to the lily family members, especially members of Amaryllidaceae that also have a 3-parted stigma, 6 prominent stamens and 6 tepals.
If you haven’t already read my articles on plant identification and scientific names, I recommend reading those to get a broader picture of the topic. Alternatively, you can browse some of my other plant families, subfamilies and genera below.