Layered Clothing
Fashion Terms

Why should I wear several layers of shirts?

Did your mother tell you to make sure to layer up today?

Layered clothing is a term describing a way of dressing using many garments that are worn on top of each other.  Some of the layers have different, largely non-overlapping, functions.  Using more or fewer layers, or replacing one layer but not others, allows for flexible clothing to match the needs of each situation.  Two thin layers can be warmer yet lighter than one thick layer, because the air trapped between layers serves as thermal insulation. Layered clothing is particularly relevant in cold climates, where clothing must at the same time transfer moisture (wicking), provide warmth, and protect from wind and rain.  

Outdoor and sportswear manufacturers favor layered clothing because, among other reasons, it allows them to offer so-called "technical" or "functional" clothes which are optimized for the particular demands of a specific layer.  Such clothes are often made of advanced synthetic materials, and can be expensive.

Another benefit to wearing multiple layers of clothing is that if you become too warm, you can reduce layers as appropriate.

Put on a t-shirt, then a thin sweatshirt, then put on a sweater, then put on a hoodie.  Now you are layered.