Thermal underwear encompasses a range of close-fitting insulating garments worn next to the skin, commonly used as base layers in cold weather. These versatile undergarments provide warmth through specialized fabric construction, typically featuring a waffle or grid pattern that traps air for insulation while maintaining breathability. Read more…
Thermal Underwear
‘Thermal Underwear’ is the formal, most popular and all-encompassing term for this category. It technically includes all variations of insulating undergarments and is commonly used in retail and manufacturing contexts. ‘Thermals’ is often used as casual shorthand, widely used in everyday conversation. Both versions derive from the garments’ heat-retention properties.
Long Johns
This is perhaps the most recognized colloquial term, named after boxer John L. Sullivan in the late 19th century. This term often specifically refers to two-piece sets consisting of a long-sleeved top and ankle-length bottoms.
Union Suits
A Union Suit is a specific one-piece design that covers the entire body, typically featuring a buttoned front and characteristic rear flap. While less common today, union suits maintain a dedicated following and represent an important part of cold-weather clothing history.
Long Underwear
This is the traditional way to describe the garment’s full-length design. This straightforward name remains popular, especially in North America, and clearly distinguishes these items from regular undergarments.
Base Layers
This is the modern technical term for these garments, emphasizing their role in a layered clothing system. This term is particularly common in outdoor and athletic contexts, where precise terminology helps users select appropriate gear.
These garments are available in various materials including traditional wool, modern synthetics, and natural fibers like merino and bamboo. They serve multiple purposes from everyday warmth to specialized athletic performance, making them essential items for cold weather wardrobes.
