instability

Etymology

It is inherited from Middle English instabilite,^[2][3] borrowed from Old French instabilité (“inconstancy”),^[4][5][2][6] recorded in Anglo-Norman from the second quarter of the 13th century,^[7] and partly directly from Latin īnstabilitās (“unsteadiness”),^[4][2][8] the noun of īnstabilis (“unsteady, not firm, inconstant, fickle”),^[4][5] formed from in- (“not”) and stabilis (“firm, steadfast, stable”),^[4][9] the source of stable.^[4][9] Etymonline explains stabilis as "able to stand", from a suffixed form of Proto-Indo-European *sta- (“to stand, make or be firm”).^[4]

Earliest recorded meaning

Changeableness, uncertainty: about 1422, in Hoccleve's Learn to Die, which says that very few can perceive "thinstabilitee Of the world".^[5][2]

Semantic evolution

From the start the word covered both changeableness and a lack of firmness of character or purpose; the Middle English translation of Boethius by Walton (about 1450) has the second sense.^[2] The OED's definition joins position, condition and moral qualities: a want of steadiness, fixity or firmness.^[5] Johnson (1755) gave only the moral meaning, "inconstancy; fickleness; mutability of opinion or conduct".^[10] In psychology the word has been used since 1897 for a tendency to unpredictable behaviour or erratic changes of mood.^[5] Modern dictionaries add physical insecurity, as of a building, and economic or political unrest,^[8][11] and in physics a fast-growing disturbance in a plasma.^[11]

Timeline

• c. 1422 – changeableness, in Hoccleve.^[5][2]
• c. 1450 – lack of firmness of character or purpose.^[2]
• 1755 – Johnson: inconstancy, fickleness.^[10]
• 1897 – in psychology, a tendency to erratic behaviour.^[5]

Modern meaning

Noun

1. Lack of stability or firmness; a tendency to shift or give way: Engineers were worried by the instability of the old pier.
2. Lack of steadiness in affairs; liability to sudden change: years of political instability.
3. (psychology) A tendency to unpredictable behaviour or erratic changes of mood.
4. (physics) A rapidly growing disturbance or wave in a plasma.

Related words

• instable
• stability
• stable
• unstable

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g Kurath, Hans; Kuhn, Sherman M.; Lewis, Robert E., eds. (1952–2001), Middle English Dictionary, Ann Arbor: University of Michigan Press; online edition ed. Frances McSparran et al. (2000–2018)
3. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
4. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
5. ^ a b c d e f g Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
6. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
7. ^ Anglo-Norman Dictionary (AND2), Aberystwyth University, anglo-norman.net (2nd ed., 2005–)
8. ^ a b Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
9. ^ a b Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
10. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
11. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins