surprisal/sə(ɹ)ˈpɹaɪzəl/EtymologyFrom surprise + -al. (information measure): Defined by Myron Tribus in the 1961 book Thermostatics and Thermodynamics.nounA surprise attack or ambush; a sudden or unexpected assault.“Their chiefe attempts are by Stratagems, trecheries, or surprisals.”A sudden coming-upon someone or something unexpectedly or unawares.“How to secure the lady from surprisal”A surprising event or occurrence.The feeling caused by being surprised; surprise, shock, amazement.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.“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.”