theta; Θ, θ +

(Greek: the eighth letter of the Greek alphabet; Θ, θ; theta symbol, ϑ)

The eighth letter of the Greek alphabet (Θ, θ, ϑ), represented in the English alphabet as "th".

Equivalent in classical Greek to t + h, as in "right-hand", but in modern Greek to spirant th, as in "thin".

theta antigen
A cell membrane constituent which distinguishes T cells from other lymphocytes.
theta pinch
In physics, a plasma fusion device that operates with a high degree of stability.

It utilizes the magnetic field generated by its own currents, which are induced by pulsing, to confine the plasma for several microseconds.

The device is configured so that the self-generated magnetic field runs parallel to a longitudinal axis.

theta polarization
Polarizatin in which the electric field vector is tangent to meridian lines of some specified spherical frame of reference.
theta rhythm, theta wave
1. A pattern of brain waves having a regular frequency of 4 to 7 cycles per second as recorded by an electroencephalograph, observed during various states of light sleep or arousal.

It occurs naturally in children up to about 12 years of age, but it is considered abnormal in adults.

2. The normal brainwave in the encephalogram of a person who is awake but relaxed and drowsy.

It occurs with low frequency and low amplitude.

3. A relatively high amplitude brain wave pattern between approximately 4 and 9 hertz that is characteristic; especially, of the hippocampus but occurs in many regions of the brain including the cortex.
theta temperture
In polymer solutions, the temperature at which the second virial coefficient disappears and the coiled polymer molecules expand to their full contour length and become rod-shaped.
A plot of the temperature as a function of pressure for a thermodynamic system.
1. A general term for electronic navigation systems that determine a position based on bearings from transmitters located at different, but accurately known positions.
2. The generic term for electronic navigation systems in which a position is derived by calculations based on the bearing from two, or more, emitters located at different but accurately known positions.

You can see all of the letters of the Greek Alphabet on this page.