English Reference
adjective · noun

thermal

adj. · n.
US /ˈθɝməɫ/ UK /θˈɜːməl/ ther·mal

  1. 01 B2 Upper Intermediate Technical Science

    adj.relating to heat or temperature.

    adj.pertaining to heat, temperature, or the movement of heat energy.

    Simple

    The scientists measured the thermal energy produced by the chemical reaction.

    In context

    The spacecraft was equipped with a specialized shield to withstand the extreme thermal stress of atmospheric reentry.

    caloricheat related
  2. 02 B2 Upper Intermediate

    adj.designed to keep you warm by trapping heat, especially clothes.

    adj.providing efficient thermal insulation to maintain body temperature in cold environments.

    Simple

    You should wear thermal underwear if you are going skiing in the mountains.

    In context

    The hikers invested in high-quality thermal layers to ensure they remained warm during the overnight trek across the glacier.

  3. 03 C1 Advanced Technical

    n.a column of rising warm air that birds and gliders use to stay high in the sky.

    n.a column of rising air in the lower atmosphere created by the uneven heating of the earth's surface.

    Simple

    The eagle circled higher and higher as it caught a strong thermal.

    In context

    The glider pilot searched for a thermal over the sun-baked fields to gain enough altitude for the return journey.

    updraftconvection current
  4. 04 C1 Advanced Technical Military

    n.a type of camera or sensor that sees heat instead of light.

    n.an infrared imaging device or sensor used to detect heat signatures, often in low-visibility conditions.

    Simple

    The rescue team used a thermal to find the lost hikers in the dark woods.

    In context

    The surveillance drone was equipped with a high-resolution thermal to detect movement through the dense forest canopy at night.

    infraredFLIR

Usage thermal comfort

As seawater warms it expands, and this thermal expansion accounts for roughly a third of sea level rise recorded by scientists to date.

BBC News· 10 Aug 2026

But he says that will only give you the perception of "thermal comfort" - in other words you will feel cooler but you're not actually cooling as much as you might think.

BBC News· 8 Jul 2026

From French thermal, from New Latin thermalis, from Ancient Greek θέρμη (thérmē, “heat”), from Proto-Indo-European gʷʰer- (“to heat, warm”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin ine-pro *gʷʰer-
Level C1 · Advanced
Frequency Common
Updated