imaginary

Etymology

It is borrowed from Latin imāginārius (“consisting of a mere semblance, unreal, fictitious”),^[2][3][4] formed with the suffix -ārius (English -ary) on imāgō (“image”).^[2][5][6] In post-classical Latin the adjective also meant "concerning images" (early 4th century) and "of the imagination" (from the 12th century in British sources), and as a noun it named a standard-bearer (4th century).^[2] Etymonline also allows that it may have been formed in English from imagine and -ary.^[7] Johnson (1755) gave its source as imaginaire.^[8]

Earliest recorded meaning

Existing only in imagination or fancy; not real: a1425, in the later version of the Wycliffite Bible.^[2] Etymonline dates imaginarie to the late 14th century, and Dictionary.com to 1350–1400.^[7][6]

Semantic evolution

Early senses also included "existing only as spirit, not bodily", now obsolete.^[2] From 1541 the word described a line or circle assumed to pass through certain points but otherwise not existing.^[2][4] Several 16th- and 17th-century senses died out: of the nature of an image (1594–1671, first in Shakespeare's Lucrece), imaginable (1624–1862), and supposed, putative (a1631–1803).^[2][9] Johnson (1755) defined it as "fancied; visionary; existing only in the imagination".^[8] In mathematics Isaac Newton used it in 1670 for a quantity expressed through the square root of a negative number,^[2] and the noun imaginary, such a quantity, follows in 1768.^[2] The noun had earlier meant a Roman officer who carried the emperor's image (a1460) and a fancy, something imagined (1594).^[2] Imaginary friend is attested by 1789.^[7]

Timeline

• a1425 – existing only in the imagination.^[2]
• a1460 – noun, an officer who carried the emperor's image (obsolete).^[2]
• 1541 – of a line or circle, assumed but not physically real.^[2]
• 1594 – noun, something imagined.^[2]
• 1670 – (mathematics) involving the square root of a negative quantity.^[2]
• 1768 – noun, (mathematics) an imaginary quantity.^[2]
• 1789 – imaginary friend.^[7]

Modern meaning

Adjective

1. Existing only in the imagination; not real: The child chatted away to an imaginary companion.
2. Of a line or point, assumed for the purposes of description but having no physical existence: an imaginary line between the two peaks.
3. (mathematics) Involving or being an imaginary number, a multiple of the square root of −1.

Noun

1. (mathematics) An imaginary quantity or complex number.

Word family

• imaginarily
• imaginariness
• imaginary number
• imaginary unit

Related words

• image
• imagine
• imaginative
• imagination

Usage notes

Dictionary.com lists imaginative as a word often confused with imaginary.^[6]

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
4. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
6. ^ a b c Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
7. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
8. ^ 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.
9. ^ Kay, Christian; Roberts, Jane; Samuels, Michael; Wotherspoon, Irené, eds. (2009), Historical Thesaurus of the Oxford English Dictionary, Oxford: Oxford University Press; online edition (2024)