Squashes generally refer to four species of the genus Cucurbita, also called marrows depending on variety or the nationality of the speaker. These species include C. maxima (hubbard squash, buttercup squash, some varieties of prize pumpkins, such as Big Max), C. mixta (cushaw squash), C. moschata (butternut squash), and C. pepo (most pumpkins, acorn squash, summer squash, zucchini). In North America, squash is loosely grouped into summer squash or winter squash, depending on whether they are harvested as immature fruit (summer squash) or mature fruit (autumn squash or winter squash). Gourds are from the same family as squashes. Well known types of squash include the pumpkin and zucchini. Giant squash are derived from Cucurbita maxima and are routinely grown to weights nearing those of giant pumpkins. For more details, refer to list of gourds and squashes.

Archaeological evidence suggests squash may have been first cultivated in Mesoamerica some 8,000 to 10,000 years ago, and may have been independently cultivated elsewhere at a later date. Squash was one of the "Three Sisters" planted by Native Americans. The Three Sisters were the three main native crop plants: maize (corn), beans, and squash. These were usually planted together, with the cornstalk providing support for the climbing beans, and shade for the squash. The squash vines provided ground cover to limit weeds. Weeds can be detrimental to the growing conditions of the squash. The beans provided nitrogen fixing for all three crops.

Squash may refer to:

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as flowering plants, conifers, ferns, mosses, and green algae, but do not include seaweeds like kelp, nor fungi and bacteria. The group is also called green plants or Viridiplantae in Latin. They obtain most of their energy from sunlight via photosynthesis using chlorophyll contained in chloroplasts, which gives them their green color. Some plants are parasitic and may not produce normal amounts of chlorophyll or photosynthesize.

Precise numbers are difficult to determine, but as of 2010^[update], there are thought to be 300–315 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants (see the table below).

The scientific study of plants is known as botany.

Plants are one of the two groups into which all living things have been traditionally divided; the other is animals. The division goes back at least as far as Aristotle (384 BC – 322 BC) who distinguished between plants which generally do not move, and animals which often are mobile to catch their food. Much later, when Linnaeus (1707–1778) created the basis of the modern system of scientific classification, these two groups became the kingdoms Vegetabilia (later Metaphyta or Plantae) and Animalia (also called Metazoa). Since then, it has become clear that the plant kingdom as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these organisms are still often considered plants, particularly in popular contexts.