thermals

IPA/ˈθɜː.məl/
IPA/ˈθɝː.məl/

thermals — noun

1. Warm undergarments made from special fabric that holds body heat close to the sk

1.nounB2
Definition

Warm undergarments made from special fabric that holds body heat close to the skin, worn beneath everyday clothes in very cold weather.

Example

Yuna packed two pairs of thermals for the skiing holiday in the Austrian Alps.

a pair of thermals / two pairs of thermals — unit collocation

Arjun wore thin silk thermals under his work trousers during the freezing winter months.

Common collocations
  • wear thermals
  • put on thermals
  • a pair of thermals
  • a set of thermals
  • silk thermals
  • wool thermals
  • lightweight thermals
Synonyms
  • long johns

    informal term for one-piece or two-piece thermal underwear; older-fashioned connotation

  • base layer

    modern sportswear term; broader category that includes thermals but also non-thermal wicking garments

  • thermal underwear

    the full formal term; 'thermals' is the shortened everyday form

Grammar Patterns

wear thermals

a set of thermals

a pair of thermals

Usage Note

Plural noun — you cannot say 'a thermal' to mean a single piece of thermal underwear. Use 'a pair of thermals' for one set (top and bottom) or 'a thermal top' / 'a thermal vest' for a single garment. The adjective form 'thermal' (e.g. thermal leggings, thermal shirt) is very common and often preferred in product descriptions.

Common Mistakes

I bought a thermal yesterday.
I bought a pair of thermals yesterday.
The noun 'thermals' is always plural when referring to the clothing.
These thermals are so thin you can see through them.
These thermal leggings are so thin you can see through them.
For a single garment item, use 'thermal' as an adjective + the garment name.

2. A rising stream of warm air that lifts upwards from sun-heated ground or water,

2.nounB2
Definition

A rising stream of warm air that lifts upwards from sun-heated ground or water, which birds and pilots of light aircraft use to gain height without using engine power.

Example

Pedro spotted a hawk circling higher and higher as it caught the afternoon thermal above the valley.

the thermal (singular); birds ride thermals to gain altitude

Paragliders launch early because thermals grow strongest once the sun has warmed the ground for hours.

thermals are strongest — typical collocation with 'strong' / 'weak'

Common collocations
  • ride a thermal
  • catch a thermal
  • strong thermals
  • thermals form
  • look for thermals
  • search for thermals
Synonyms
  • updraft

    broader term for any upward-moving air current, which may be caused by wind hitting a slope or by heat; 'thermal' specifically means heat-driven updraft

  • rising current

    descriptive phrase rather than a single-word synonym; less technical than 'thermal'

Antonyms
  • downdraft

    a descending current of cold air, the opposite of a thermal updraft

  • sink

    glider pilot term for a region of sinking air; the opposite of finding a thermal

Grammar Patterns

thermals + verb (form)

a thermal / the thermal (singular context)

Usage Note

Used especially in aviation, meteorology, and bird-watching contexts. The singular form 'a thermal' is common when referring to one specific column of rising air; 'thermals' is the general plural. Birds such as eagles, hawks, and vultures are famous for riding thermals to conserve energy during long-distance flight.

Common Mistakes

I felt a thermal of hot air in my room.
I felt a draft of hot air in my room.
'thermal' as a noun in everyday English specifically means a rising outdoor air column, not any hot air indoors.
The plane flew into thermals and shook.
The glider hit a thermal and rose sharply.
Large commercial planes do not ride thermals; this term belongs to gliders, birds, and paragliders.

thermals — adjective

Word family

Synonym discussion

Sense: noun/1

'Thermals' is the everyday, shortened form of 'thermal underwear' and covers any insulating garment worn under regular clothes — typically a top and bottom set. 'Long johns' is an older, more informal term, often associated with one-piece or two-piece buttoned undergarments from decades past; younger speakers may find it old-fashioned. 'Base layer' is the modern sportswear term, broader in scope because it refers to the first layer of clothing against the skin regardless of whether it is thermal or just moisture-wicking. 'Thermal underwear' is the full formal name and is interchangeable with 'thermals' in most contexts, though it sounds slightly more clinical or descriptive. In a sentence: 'Arjun put on his thermals before the ski run, while his sister wore a modern base layer made of synthetic fabric — both kept them warm, but only the thermals were thick enough for the chairlift in minus ten degrees.'

thermals ↗long johns ↗base layer ↗thermal underwear

Common collocations

Phrases

  • ride thermals
  • catch a thermal
  • wear thermals
  • a pair of thermals
  • thermal energy
  • thermal conductivity
  • thermal expansion
  • thermal imaging
  • thermal insulation
  • thermal vest
  • thermal socks
  • thermal spring
  • thermal water
  • thermal pool

Etymology

GreekLatinFrenchEnglish

The word 'thermal' comes from the Greek 'thermē' (heat), which passed into Latin as 'thermae' (hot springs, warm baths) and then into French as 'thermal'. English borrowed the adjective 'thermal' in the mid-1700s to describe anything related to heat. The plural noun 'thermals' developed two separate meanings in the 20th century: glider pilots in the 1930s began using 'thermals' to describe columns of rising warm air (the 'thermal' updraft), and clothing manufacturers in the 1940s used 'thermal' to market insulating fabric that trapped body heat, which people soon referred to as 'thermals' for short.

First known use

1742

1742, in the meaning defined at sense 3 Noun