See Also: Theta(medicine)
Theta(money)
Theta(finance)
rho-theta(dictionary)
theta(dictionary)
theta antigen(medicine)
theta pinch(medicine)
theta rhythm(medicine)
theta wave(medicine)

theta (iou)



theta noun. LME.
[Greek theta.]
The eighth letter (?, ?) of the Greek alphabet, also used in transliterating other languages; transf. a sign of doom, a death sentence (in allus. to the custom of using ? as standing for thanatos 'death' on the ballots used in voting on a sentence of life or death in ancient Greece). Also, the phonetic symbol ?, used spec. in the International Phonetic Alphabet to represent a voiceless dental fricative. LME.
Chemistry. Used attrib. to designate the temperature of a polymer solution at which it behaves ideally as regards its osmotic pressure (also ? temperature, ? temperature), and the conditions, solvent, etc., associated with such behaviour. M20.
Particle Physics. A meson that decays into two pions, now identified as a kaon. Also theta meson, ?-meson. M20.
Comb.: theta activity, theta rhythm, theta waves electrical activity observed in the brain under certain conditions, consisting of oscillations having a frequency of 4 to 7 hertz; theta-function Math. (a) the sum of a series from n= to n=+ of terms denoted by exp(n2a+2na); a similar function of several variables; (b) a function occurring in probabilities, expressed by the integral exp(t2)dt; theta meson: see sense 3 above; theta-phi diagram a temperature-entropy diagram, which represents the heat-units converted into work per pound of working fluid (? = absolute temperature; ¦Õ = entropy); theta pinch Physics a toroidal pinch (PINCH noun 1d) in which the magnetic field follows the axis of the plasma and the current-carrying coils encircle it; theta rhythm, theta waves: see theta activity above.