theta

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the·ta / ˈ[unvoicedth]ātə; ˈ[unvoicedth]ē-/ • n. the eighth letter of the Greek alphabet (Θ, θ), transliterated as ‘th.’ ∎  (Theta) [followed by Latin genitive] Astron. the eighth star in a constellation: Theta Draconis. ∎  [as adj.] Chem. denoting a temperature at which a polymer solution behaves ideally as regards its osmotic pressure. ∎  [as adj.] denoting electrical activity observed in the brain under certain conditions, consisting of oscillations having a frequency of 4 to 7 hertz: theta rhythm.• symb. ∎  (θ) temperature (esp. in degrees Celsius). ∎  (θ) a plane angle. ∎  (θ) a polar coordinate. Often coupled with φ.

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