simplex

Etymology

It is borrowed from Latin simplex (“single, simple, plain, unmixed”).^[2][3][4][5] The Latin adjective is literally "one-fold",^[3][6][7] from sim- (“one”) and -plex (“-fold”),^[6][7] and these go back to Proto-Indo-European *sem- (“one; as one, together with”) and *plek- (“to plait”).^[3][5] The Shorter Oxford takes it as a variant of simplus (“simple”), the source of simple, with the second element of duplex and multiplex,^[8][9] and the OED likewise refers it to that adjective.^[2]

Earliest recorded meaning

Having a single part, not composite: before 1398, in John Trevisa's translation of Bartholomaeus Anglicus, in the OED's entry revised in 2019.^[2] Barnhart and Merriam-Webster Unabridged date the adjective to 1594, Etymonline to the 1590s and the Shorter Oxford to the late 16th century.^{[4][10][3][8]}

Semantic evolution

The OED now finds the general sense somewhat rare.^[2] In telegraphy, from 1876, it meant a line carrying signals in one direction at a time, as against duplex.^[2][8][7] In linguistics the noun for a word without an affix dates from 1731, in the revised OED, though Barnhart and Etymonline give 1892;^[2][4][3] the adjective is recorded from 1890, and in transformational grammar the noun meant a kind of simple sentence from 1960.^[2] In genetics it was used from 1908 of an eye with pigment on only one surface of the iris, and since 1911 for a certain makeup of alleles at one locus.^[2] In mathematics the noun named the simplest figure of a given number of dimensions, from 1905 in the OED and 1914 in Barnhart.^[2][4] In the United States a simplex apartment, on one floor, contrasts with a duplex: the adjective is recorded from 1909 and the noun from 1912.^[2]

Timeline

• before 1398 – having a single part, not composite.^[2]
• 1731 – noun, a simple or uncompounded word.^[2]
• 1876 – of a line or system, carrying signals in one direction at a time.^[2]
• 1905 – noun, a triangle, tetrahedron or a similar figure in any dimension.^[2]
• 1908 – of an eye, with pigment on one surface of the iris only.^[2]
• 1909 – of an apartment, on one floor; as a noun from 1912.^[2]
• 1960 – noun, in transformational grammar, a simple sentence.^[2]

Meanings

Adjective

1. Having a single part or element; not composite.^[2][5][10]
2. Of a telecommunications or computing system: sending signals in only one direction at a time.^[7][2][6]
3. Of a word: simple, not compound, with no affix.^[2]
4. In genetics, of a polyploid: having one copy of the dominant form of a gene.^[10][8][2]
5. Chiefly in the United States, of an apartment: on one floor only.^[2]

Noun

1. A simple word, as against a compound.^[7][10][2]
2. In geometry, the most elementary figure of a given number of dimensions, as a line segment in one and a triangle in two.^[7][5][2]
3. A method of telecommunication in only one direction at a time.^[10]
4. Chiefly in the United States, an apartment on one floor.^[2]

Verb

1. To make simplex.^[10]

Word family

• simplex method

Related words

• herpes simplex
• simplicial
• simple
• duplex
• multiplex
• complex

Usage notes

The plural is simplexes, or in mathematics and technical use also simplices or simplicia.^[7][10][5]

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 q r s t u v w x y 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 c d Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b c d e The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
6. ^ a b c Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
7. ^ a b c d e f g Collins English Dictionary (2023), Glasgow: HarperCollins
8. ^ 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
9. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
10. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster