surprisal

English

Etymology

Etymology tree

English surprise

Proto-Indo-European *h₂el-

Proto-Indo-European *-is

Proto-Indo-European *h₂élisder.?

Proto-Italic *-ālis

Latin -ālisbor.

Old French -albor.

▲

Latin -ālis

Old French -elbor.

▲

Latin -ālisbor.

Middle English -al

English -al

English surprisal

From surprise + -al.

(information measure): Defined by Myron Tribus in the 1961 book Thermostatics and Thermodynamics.

Pronunciation

• IPA^(key): /sə(ɹ)ˈpɹaɪzəl/

Noun

surprisal (countable and uncountable, plural surprisals)

1. (obsolete, military) A surprise attack or ambush; a sudden or unexpected assault. [16th–19th c.]
   • 1624, John Smith, Generall Historie, Kupperman, published 1988, page 146:

     Their chiefe attempts are by Stratagems, trecheries, or surprisals.

2. (obsolete) A sudden coming-upon someone or something unexpectedly or unawares. [17th c.]
   • 1646 (indicated as 1645), John Milton, “Comus”, in Poems of Mr. John Milton, […], London: […] Ruth Raworth for Humphrey Mosely, […], →OCLC:

     How to secure the lady from surprisal

   • a. 1678 (date written), Isaac Barrow, “(please specify the chapter name or sermon number)”, in The Works of Dr. Isaac Barrow. […], volume (please specify |volume=I to VII), London: A[braham] J[ohn] Valpy, […], published 1830–1831, →OCLC:

     Because death is uncertain, let us prevent its surprisal.

3. (obsolete) A surprising event or occurrence. [17th–19th c.]
4. (obsolete) The feeling caused by being surprised; surprise, shock, amazement. [17th–19th c.]
5. An information measure as equal in bits (binary digits) to the base-2 log of 1 over the probability, with the result that the number of choices equals 2ⁿ where n is the number of bits.

   Synonym: Shannon information

   • 2025, Edward A. F. Gibson, “Preliminaries: Components of Language Structure” (chapter 2), in Syntax: A Cognitive Approach, MIT Press, →DOI, →ISBN, pages 23–24:

     Because language is produced and processed over time, we get it bit by bit. This allows a measure of the goodness of an incoming word according to how expected it was, given the preceding context: its expectedness or surprisal. Surprisal and expectedness are inverses: When an incoming word is highly expected, its surprisal is close to zero.

See also

• surprisal on Wikipedia.Wikipedia