A sweater is a knitted garment worn on the upper body for warmth. It is usually made of wool, cotton, or synthetic fibers, though cashmere, alpaca, and mohair are used in luxury versions. The knit structure traps air, which insulates. A sweater is warmer than a woven shirt of the same weight because of that trapped air.

Types are numerous. The pullover goes over the head. The cardigan opens in the front. The crew neck has a round neckline. The V-neck dips. The turtleneck covers the neck. The mock neck is shorter. The cable knit uses twisted patterns for texture. The Fair Isle sweater uses multiple colors in patterned bands. The Aran sweater originates from the Irish islands and features complex stitch patterns. The fisherman's sweater is thick and practical. Each has its own history and look.

Materials affect care and feel. Wool is warm, durable, and naturally odor-resistant. Merino wool is softer and finer than standard wool. Cashmere is very soft but pills easily. Cotton is breathable but less warm. Acrylic is cheap and machine washable but can pill and hold static. Blends combine fibers for cost and performance. Care is important. Wool sweaters should be hand washed or dry cleaned. They should be dried flat to avoid stretching. Pilling can be removed with a fabric shaver. Storing folded rather than hung prevents shoulder distortion. A good sweater can last for many seasons.

Common types

• Crew neck
• V-neck
• Turtleneck
• Cable knit
• Fair Isle and Aran