entry

n 1: an item inserted in a written record

2: the act of beginning something new; "they looked forward to

the debut of their new product line" [syn: {debut}, {first

appearance}, {launching}, {unveiling}, {introduction}]

3: a written record of a commercial transaction [syn: {ledger

entry}]

4: a message submitted in a competition [syn: {submission}]

5: something that allows entry or exit; "they waited at the

entrance to the garden"; "beggars waited just outside the

entryway to the cathedral" [syn: {entrance}, {entranceway},

{entryway}, {entree}]

6: the act of entering; "she made a grand entrance" [syn: {entrance},

{entering}, {ingress}, {incoming}]

entropy

A measure of the disorder of a system. Systems tend

to go from a state of order (low entropy) to a state of

maximum disorder (high entropy).

The entropy of a system is related to the amount of

{information} it contains. A highly ordered system can be

described using fewer {bit}s of information than a disordered

one. For example, a string containing one million "0"s can be

described using {run-length encoding} as [("0", 1000000)]

whereas a string of random symbols (e.g. bits, or characters)

will be much harder, if not impossible, to compress in this

way.

{Shannon}'s formula gives the entropy H(M) of a message M in

bits:

H(M) ◦ -log2 p(M)

Where p(M) is the probability of message M.

(1998-11-23)