Noun

(en noun)

an increase in density; the act of compressing, or the state of being compressed; compaction

the cycle of an internal combustion engine during which the fuel and air mixture is compressed

(computing) the process by which data is compressed

* {{quote-web

, year = 2011 , author = Marcelo A. Montemurro & Damián H. Zanette , title = Universal Entropy of Word Ordering Across Linguistic Families , site = PLoS ONE , url = http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0019875 , accessdate = 2012-09-26}}

Due to the presence of long-range correlations in language [21], [22] it is not possible to compute accurate measures of the entropy by estimating block probabilities directly. More efficient nonparametric methods that work even in the presence of long-range correlations are based on the property that the entropy of a sequence is a lower bound to any lossless compressed version of it [15]. Thus, in principle, it is possible to estimate the entropy of a sequence by finding its length after being compressed by an optimal algorithm. In our analysis, we used an efficient entropy estimator derived from the Lempel-Ziv compression algorithm that converges to the entropy [19], [23], [24], and shows a robust performance when applied to correlated sequences [25] (see Materials and Methods).

(music) the electronic process by which any sound's gain is automatically controlled

(astronomy) the deviation of a heavenly body from a spherical form

Noun

(lb) An area that is lower in topography than its surroundings.

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*:It was not far from the house; but the ground sank into a depression there, and the ridge of it behind shut out everything except just the roof of the tallest hayrick. As one sat on the sward behind the elm, with the back turned on the rick and nothing in front but the tall elms and the oaks in the other hedge, it was quite easy to fancy it the verge of the prairie with the backwoods close by.

(lb) In psychotherapy and psychiatry, a state of mind producing serious, long-term lowering of enjoyment of life or inability to visualize a happy future.

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(lb) In psychotherapy and psychiatry, a period of unhappiness or low morale which lasts longer than several weeks and may include ideation of self-inflicted injury or suicide.

(lb) An area of lowered air pressure that generally brings moist weather, sometimes promoting hurricanes and tornadoes.

(lb) A period of major economic contraction.

Four consecutive quarters of negative, real GDP growth. See NBER.

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A lowering, in particular a reduction in a particular biological variable or the function of an organ, in contrast to elevation.