Prefix · heat / temperature
Signals relation to heat or temperature: thermometer, thermostat, thermodynamics, thermal.
Written by Bryan López, English teacher · Updated
Thermo- comes from Greek "therme" (heat) and signals a relation to heat or temperature: thermometer = an instrument to measure temperature; thermostat = a device that regulates temperature automatically; thermodynamics = the science studying heat and energy; thermal = related to heat. It is the prefix of heat in the sciences.
Thermo- appears across multiple fields: thermoplastic = a plastic that can be moulded by heat; thermonuclear = a nuclear reaction requiring extreme heat (as in the sun or hydrogen bombs); thermosphere = the hot upper layer of the atmosphere; thermocouple = an industrial temperature sensor. In earth science, "geothermal" combines geo- and thermal to signal the Earth's internal heat.
Attaches to scientific and technical nouns. Spanish equivalent is "termo-":
Pronunciation: /ˈθɜːrməʊ/, with the voiceless "th" as in "think." Spanish equivalent: "termo-" (termómetro, termostato). The spelling difference is purely orthographic; the meaning is the same.
thermo-/ˈθɜːrməʊ/
Tap the button to hear how the prefix sounds. Each word in the table has its own audio.
"Thermometer" only measures (it observes). "Thermostat" measures AND acts: it switches heating or cooling systems on and off automatically when the temperature crosses a set threshold.
"Thermal" is a broad adjective meaning "relating to heat": thermal energy, thermal imaging (infrared cameras), thermal underwear (retains body heat), thermal baths (hot spring water). It is not limited to spa contexts.
A trick to remember it
Thermo- = "heat": thermometer = measures heat/temperature, thermostat = controls heat/temperature automatically, thermodynamics = the science of heat and energy. In Spanish it is "termo-" (termómetro = thermometer). Only the spelling of the prefix changes; the meaning is the same.
Exercise 1 · Form the word
Exercise 2 · Pick the right one
"Adjust the ___ to eighteen degrees and the system will maintain that temperature automatically."
Exercise 3 · Pick the right one
What is the difference between "thermometer" and "thermostat"?
The prefix thermo- signals relation to heat or temperature: thermometer, thermostat, thermodynamics, thermal. In Spanish it usually maps to termo-.
The prefix thermo- is pronounced /ˈθɜːrməʊ/. For example, "thermometer".
"meter" becomes "thermometer". It is a typical example of the thermo- prefix.
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