predictability

Etymology

It is formed from English predictable + -ity.^[2][3] The OED notes that it follows the pattern of the suffix -bility.^[2] Predictable is formed from the verb predict and -able, and is recorded from 1820;^[2][3] the verb comes from Latin praedictus, the past participle of praedīcō (“to say beforehand, foretell”), formed from prae- (“before”) and dīcō (“to say”).^[2][3][4]

Earliest recorded meaning

The quality or character of being predictable: 1855, according to Etymonline.^[3] The OED's first quotation is from 1868, in A. Bain's Mental and Moral Science.^[2]

Semantic evolution

The word has kept the sense of its adjective: the OED defines it both as the condition of being predictable and as the degree to which something can be foreseen or used to forecast something else.^[2] The adjective predictable had come to be used of people who behave as expected, and later sometimes with a disparaging note of being tiresomely unsurprising.^[2][5]

Timeline

• 1855 – the quality of being predictable.^[3] The OED's first quotation is from 1868.^[2]

Meanings

Noun

1. The quality or state of being predictable: The predictability of the tides made the harbour easy to use.^[4][2][1]
2. The degree to which something can be predicted or used to make predictions.^[2]

Related words

• predictable
• predict
• prediction
• unpredictability

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
5. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press