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

Deep awareness of the suffering of another, coupled with the wish to relieve it

* 1849 , Robert Leighton (Archbishop of Glasgow), A practical commentary upon the first Epistle of St. Peter (page 47)

Oh! the unspeakable privilege to have Him for our Father, who is the Father of mercies and compassions , and those not barren, fruitless pityings, for He is withal the God of all consolations.