theta

noun

1. 1

   The eighth letter of the Modern Greek alphabet, ninth in Old Greek: Θ, θ.

2. 2

   The measure of an angle.

3. 3

   Pitch angle; the angle between an aircraft's longitudinal axis and the horizontal plane.

4. 4

   The sensitivity of the value of a derivative with respect to time; the "time decay".

5. 5

   Designating a level of brain activity as measured by electroencephalography having a frequency of between four and seven cycles per second (associated with drowsiness in adults).

   The reader is less likely to throw the book down in a fit of disgust than she is to be lulled into a theta state, a highway hypnosis induced by page after page of incantatory prose.

6. 6

   The voiceless dental fricative represented by θ.

Forms

plural

thetas