Theory

In math, proof. In science, a well-tested explanation. In common use, a guess or a belief. To each their own evidence.

How We Say It

THEER·ee (common)
THEE·uh·ree (also common)

Where It Comes From

Greek theoria — looking at, contemplation, speculation. From theoros — spectator. Related to theater — both involve looking. Originally meant careful observation and contemplation before acquiring its scientific and philosophical meanings.

How It's Been Used

'It's just a theory' exploits the gap between the scientific and everyday meanings. In science, a theory is an explanation supported by extensive evidence — evolution, gravity, germ theory. In common use, theory means a guess. The gap is exploited systematically to undermine scientific consensus.

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