Prefix · heat / temperature
From Greek "thermē" (heat): appears in words about heat and temperature, like thermometer and thermostat.
Written by Bryan López, English teacher · Updated
Therm- (or thermo-) comes from the Greek therme, which means "heat". It is one of the most useful scientific prefixes: it appears in thermometers, in hypothermia, in the flask where you carry your coffee and in many other everyday and academic contexts.
Therm- and thermo- are the same root in two forms: therm- usually appears before a vowel and thermo- before a consonant. You will see the root in medicine, in home products and in school science. Even the best-known brand of insulated flasks carries it, which is why many people say "a thermos" for any flask.
Therm- / thermo- combines with other roots to describe heat, temperature, and thermal energy:
"Exothermic" describes a chemical reaction that releases heat (exo- = outside); "endothermic" describes one that absorbs heat (endo- = within). These are essential terms in chemistry and biology.
therm-/θɜːrm/
Tap the button to hear how the prefix sounds. Each word in the table has its own audio.
"Thermal underwear" retains body heat in cold weather — the word relates to temperature regulation, not just warmth. "Hypothermia" is also built on this root, describing dangerously low temperature.
A trick to remember it
Think of a thermometer, which measures heat: therm- = heat. thermometer, thermal.
Exercise 1 · Form the word
Exercise 2 · Pick the right one
When a person's core body temperature drops dangerously low due to cold exposure, the condition is called ___.
The prefix therm- from Greek "thermē" (heat): appears in words about heat and temperature, like thermometer and thermostat.
The prefix therm- is pronounced /θɜːrm/. For example, "thermometer".
"ometer" becomes "thermometer". It is a typical example of the therm- prefix.
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