unpredictable

Etymology

It is formed from English un- + predictable.^[2][3][4][5] The adjective predictable, recorded from 1820, is from predict and -able,^[3][2] and predict goes back to Latin praedīcō (“to say beforehand, foretell”), from prae- (“before”) and dīcō (“to say”).^[2][3]

Earliest recorded meaning

Not predictable; difficult or impossible to foresee: 1840, in The Dial.^[2][6][3] Dictionary.com dates the word to 1855–60.^[5]

Semantic evolution

The word followed predictable by twenty years.^[3][2] It was used as a noun, with the, for whatever cannot be predicted, from 1859, in Alexander Bain's The Emotions and the Will, and later also for a single unpredictable event or thing;^[2][6] the Shorter Oxford dates the noun only to the mid 20th century.^[4] The derivative unpredictability is recorded from the early 20th century, and unpredictably and unpredictableness from the mid 20th century.^[4]

Timeline

• 1820 – predictable.^[3][2]
• 1840 – unpredictable, adjective.^[2][6][3]
• 1859 – noun, the unpredictable.^[2][6]
• early 20th century – unpredictability.^[4]

Meanings

Adjective

1. Not able to be predicted or foreseen: The weather in the mountains is unpredictable.^[6][7][8][2]
2. Likely to change or behave in ways that cannot be foreseen; changeable.^[7][8]

Noun

1. An unpredictable person, thing or event; also, with the, whatever cannot be foreseen.^[6][8][2]

Word family

• unpredictability
• unpredictably

Related words

• unpredicted
• predict

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins
8. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt