The cucumber is a creeping vine that roots in the ground and grows up trellises or other supporting frames, wrapping around supports with thin, spiraling tendrils. The plant has large leaves that form a canopy over the fruit. The fruit of the cucumber is roughly cylindrical, elongated with tapered ends, and may be as large as 60 centimeters (24 in) long and 10 centimeters (3.9 in) in diameter. Having an enclosed seed and developing from a flower, botanically speaking, cucumbers are classified as fruits. However, much like tomatoes and squash they are often perceived, prepared and eaten as vegetables.

Cucumbers are usually more than 90% water. The sharper end of the cucumber is sometimes known as the fellbit.