simplex

See also: Simplex

English

WOTD – 18 April 2025

Etymology

A set of walkie-talkies illustrates simplex *(adjective sense 3)* wireless communication. Only one user can talk at a time while the other user listens, as the radio signal can only carry information in one direction.

The adjective is a learned borrowing from Latin simplex (“plain, simple; single”),^[1]^[2] ultimately from Proto-Indo-European *sem- (“one; together”) + *pleḱ- (“to weave”).

The noun is derived from the adjective.^[1]^[3] The plural forms simplices and simplicia are learned borrowings from Latin simplicēs (masculine or feminine) and simplicia (neuter), respectively plural forms of simplex.

Noun sense 1 (“generalization of a triangle or tetrahedron to an arbitrary dimension”) was apparently coined by the Dutch mathematician Pieter Hendrik Schoute (1846–1913) as a short version of Simplicissimum in Mehrdimensionale Geometrie (in German, 1902).^[4] (In his pioneering works on algebraic topology, the French mathematician Henri Poincaré (1854–1912) had previously introduced the concept, but not the actual term simplex.)^[5]

Pronunciation

Adjective and noun (singular form):
- (Received Pronunciation) IPA^(key): /ˈsɪmplɛks/
- (General American) IPA^(key): /ˈsɪmˌplɛks/
- Audio (Southern England): (file)
- Audio (US): (file)
- Hyphenation: sim‧plex
Noun (plural form: simplices):
- (Received Pronunciation) IPA^(key): /ˈsɪmplɪsiːz/
- (General American) IPA^(key): /ˈsɪmpləˌsiz/
- Audio (US): (file)
- Hyphenation: sim‧pli‧ces
Noun (plural form: simplicia):
- (Received Pronunciation, General American) IPA^(key): /sɪmˈplɪsiə/
- Audio (US): (file)
- Hyphenation: sim‧pli‧cia

Adjective

simplex (not comparable)

(dated) Having a single structure; not composite or complex; undivided, unitary.
Synonyms: monoplex, uniplex

Antonym: complex
(anatomy, historical) Of an eye: (supposedly) having pigment on only the posterior surface of the iris and not the anterior surface, and thus appearing blue; this was later found to be inaccurate, as eye colour is due to the amount of pigment in the anterior surface of the iris; also, of eye pigmentation: present only on the posterior surface of the iris; and of a person: having eyes with this form of pigmentation.
Antonym: duplex
(computing, telecommunications) Of a circuit or device: involving signals which travel in one direction at a time; unidirectional.
Antonyms: bidirectional, duplex

Coordinate terms: full duplex, half-duplex, semiduplex
(genetics)
1. Of a polyploid organism: having one dominant allele at a given locus on all homologous chromosomes.
  Coordinate terms: duplex, nulliplex, triplex
2. (archaic or obsolete) Synonym of heterozygous (“of an organism: having two different alleles in a given gene”)
(linguistics) Of a word: having no (derivational) affixes; simple, monomorphemic, uncompounded.
Antonym: polymorphemic
(originally and chiefly US) Of an apartment (or, sometimes, another type of property): having only one floor or storey; single-storey.
Coordinate terms: duplex, triplex

Derived terms

simplexity

Related terms

Translations

having a single structure; not composite or complex — see undivided,‎ unitary

of an eye: (supposedly) having pigment on only the posterior surface of the iris; of eye pigmentation: present only on the posterior surface of the iris; of a person: having eyes with this form of pigmentation

Macedonian: please add this translation if you can

of a circuit or device: involving signals which travel in one direction at a time — see also unidirectional

Catalan: símplex
Finnish: yksisuuntainen (fi)
Greek: μονόδρομος (el) (monódromos)
Indonesian: simplêks (id)
Macedonian: please add this translation if you can
Vietnamese: đơn công

of a polyploid organism: having one dominant allele at a given locus on all homologous chromosomes

Finnish: simpleksinen
Macedonian: please add this translation if you can

synonym of heterozygous — see heterozygous

of a word: having no affixes

Finnish: simpleksinen, johtamaton
Macedonian: please add this translation if you can

of a property: having only one floor or storey

Finnish: yksikerroksinen
Macedonian: please add this translation if you can

Noun

simplex (plural simplexes or (algebraic topology, geometry, linguistics) simplices or simplicia)

Examples (algebraic topology, geometry)
A 0-dimensional simplex is a point. A 1-dimensional simplex is a line segment. A 2-dimensional simplex is a triangle. A 3-dimensional simplex is a tetrahedron. A 4-dimensional simplex is a 5-cell.

(algebraic topology, geometry) A generalization of a triangle or tetrahedron to an arbitrary dimension, the generalization being the simplest possible convex polytope for a given dimension; more accurately, the convex hull of $n+1$ affinely independent points in $n$ -dimensional space.
(linguistics)
1. A word which is not compound and contains no derivational affixes (inflectional affixes are usually disregarded); a monomorphemic word.
  The word weak is a simplex. Its derivative weaken is not.
2. (grammar, archaic) In full simplex sentence: in transformational grammar: a simple sentence which is the product of a few transformations; a kernel sentence.
  - 1978, Helga Harries-Delisle, “Contrastive Emphasis and Cleft Sentences”, in Joseph H[arold] Greenberg, editor, Universals of Human Language, volume 4 (Syntax), Stanford, Calif.: Stanford University Press, →ISBN, page 460:
    The question is: is 139. [“Priexal Vanja. ‘arrived Vanya’”] a simplex or is it a cleft structure in which all 'superfluous' constituents were deleted. […] The only indication that 139. is a simplex is the sentence intonation and the absence of a break between the verb and the subject.
    A modified version of a paper published in Working Papers on Language Universals (November 1973), number 12, pages 85–144.
(originally and chiefly US) An apartment (or, sometimes, another type of property) having only one floor or storey; a single-storey property.
Coordinate terms: duplex, triplex

Synonyms

monoplex

Derived terms

Related terms

Translations

generalization of a triangle or tetrahedron to an arbitrary dimension, the generalization being the simplest possible convex polytope for a given dimension

Albanian: simpleks
Arabic: مُبَسَّط (ar) (mubassaṭ)
Armenian: սիմպլեքս (simplekʻs)
Basque: simplex ?
Bengali: ক্রমবর্তী সিমপ্লেক্স (kromborti śimoplekśo)
Bulgarian: симплекс (simpleks)
Catalan: símplex m
Chinese:
Mandarin: 单纯形 (dānchún xíng)
Chuvash: си́мплекс (símpleks)
Dutch: simplex (nl) ?
Finnish: simpleksi (fi)
French: simplexe (fr) m
German: Simplex (de) n
Hebrew: סימפלקס (he) m
Hungarian: szimplex (hu)
Icelandic: hyrna (is) f
Irish: aonphléacs m
Italian: simplesso (it) m
Japanese: 単体 (ja) (たんたい, tantai)
Kazakh: симплекс (simpleks)
Korean: 단체(單體) (ko) (danche)
Macedonian: please add this translation if you can
Norwegian:
Bokmål: simpleks ?

Nynorsk: please add this translation if you can
Persian: سادک (fa)
Polish: sympleks m inan
Portuguese: simplex (pt) ?, simplexo ?
Romanian: simplex (ro) n
Russian: си́мплекс (ru) m (símpleks)
Slovak: simplex ?
Slovene: simpleks ?
Spanish: símplex m
Swedish: simplex ?
Thai: ซิมเพล็กซ์
Ukrainian: симплекс m (sympleks)
Uzbek: simpleks

word which is not compound and contains no derivational affixes

Finnish: perussana
German: Simplex (de) n
Macedonian: please add this translation if you can
Swedish: simplex n

in transformational grammar: a simple sentence which is the product of a few transformations

Finnish: simpleksinen virke
Macedonian: please add this translation if you can

property having only one floor or storey

Finnish: yksikerroksinen kiinteistö
Macedonian: please add this translation if you can

References

↑ ^1.0 ^1.1 “simplex, adj. and n.”, in OED Online ⁠, Oxford: Oxford University Press, September 2024.
^ “simplex, adj.”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.
^ “simplex, n.”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.
^ P[ieter] H[endrik] Schoute (1902) “Grundbegriffe [Basic Concepts]”, in Mehrdimensionale Geometrie [Multidimensional Geometry] (Sammlung Schubert; XXXV) (in German), 1st part (Die linearen Räume [The Linear Spaces]), Leipzig, Saxony: G[eorg] J[oachim] Göschen’sche Verlagshandlung, →OCLC, paragraph 8, page 10: “Wir ziehen de namen ‚Simplicissimum‘ das viel kürzere Simplex vor und deuten das Simplex mit $d+1$ Eckpunkten mittels des Symboles $S(d+1)$ an. ― We prefer the name ‘simplicissimum’ to the much shorter simplex and indicate the simplex with $d+1$ vertices using the symbol $S(d+1)$ .”
^ Edmund [Frederick] Robertson, John O’Connor (2023 December) “SIMPLEX”, in MacTutor History of Mathematics Archive: Earliest Known Uses of Some of the Words of Mathematics‎^[1], archived from the original on 2023-12-25.

Latin

**Latin numbers ^(edit)**
	10^{[a], [b]}
	I 1	2 → ^{[a], [b], [c]}	10 → ^{[a], [b]}
Cardinal: ūnus Ordinal: prīmus Adverbial: semel Proportional: simplus Multiplier: simplex Distributive: singulus Collective: ūniō Fractional: integer

Etymology

From sem- (“one; single-”) +‎ -plex (“-fold”). The first element (from Proto-Indo-European *sem-, *sm̥-) does not occur independently in Latin, but is also seen in semel (“once”) and semper (“always, forever”). De Vaan reconstructs Proto-Italic *sm̥-plak-s,^[1] but also reconstructs Proto-Italic *-plek-s.^[2]

Pronunciation

(Classical Latin) IPA^(key): /ˈsim.pleks/, [ˈsɪmpɫ̪ɛks]
(modern Italianate Ecclesiastical) IPA^(key): /ˈsim.pleks/, [ˈsimpleks]

Adjective

simplex (genitive simplicis, comparative simplicior, superlative simplicissimus, adverb simpliciter); third-declension one-termination adjective

single
simple, plain, uncompounded
pure, unmixed
sincere, naive, frank, open, without guile, guileless, unsuspecting, innocent
- 8 CE, Ovid, Fasti 2.225–226:
  male crēditis hostī: simplex nōbilitās, perfida tēla cave!
  You do wrong to trust the enemy: Guileless nobles, beware of treacherous weapons!

Declension

Third-declension one-termination adjective.

	masc./fem.	neuter	masc./fem.	neuter
	singular		plural
nominative	simplex		simplicēs	simplicia
genitive	simplicis		simplicium
dative	simplicī		simplicibus
accusative	simplicem	simplex	simplicēs	simplicia
ablative	simplicī		simplicibus
vocative	simplex		simplicēs	simplicia

Derived terms

Related terms

Descendants

Italian: sempice, semprice, semplice (latinized)
Friulian: sempliç (latinized)
Sicilian: sìmprici, sìmplici (latinized)
→ Asturian: simple
→ Catalan: simple
→ Dutch: simpel
→ English: simplex
→ Galician: simple
→ German: simpel
- → Norwegian: simpel
→ Middle Low German: simpel
- → Old Swedish: simpel
  - Swedish: simpel
    - → Finnish: simppeli
→ Old French: simple, sinple
- French: simple
  - → Romanian: simplu
- → Middle English: symple, simple
  - Scots: semple
  - English: simple
→ Old Leonese:
- Mirandese: simples
→ Old Galician-Portuguese: simplez
- Portuguese: simples, símplice
→ Romansch: simpel, sempel
→ Spanish: simple
- Chavacano: simple
→ Proto-Brythonic: *sɨml
- Middle Welsh: symyl
  - Welsh: syml

References

^ De Vaan, Michiel (2008) “-sem-, sim-”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 553
^ De Vaan, Michiel (2008) “-plex”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 473

Romanian

Etymology

Borrowed from French simplex.

Noun

simplex n (uncountable)

simplex

Declension

Declension of **simplex**
singular only	indefinite	definite
nominative-accusative	simplex	simplexul
genitive-dative	simplex	simplexului
vocative	simplexule

[OED-1] 1.0 ^1.1 “simplex, adj. and n.”, in OED Online ⁠, Oxford: Oxford University Press, September 2024.

[2] “simplex, adj.”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.

[3] “simplex, n.”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.

[4] P[ieter] H[endrik] Schoute (1902) “Grundbegriffe [Basic Concepts]”, in Mehrdimensionale Geometrie [Multidimensional Geometry] (Sammlung Schubert; XXXV) (in German), 1st part (Die linearen Räume [The Linear Spaces]), Leipzig, Saxony: G[eorg] J[oachim] Göschen’sche Verlagshandlung, →OCLC, paragraph 8, page 10: “Wir ziehen de namen ‚Simplicissimum‘ das viel kürzere Simplex vor und deuten das Simplex mit $d+1$ Eckpunkten mittels des Symboles $S(d+1)$ an. ― We prefer the name ‘simplicissimum’ to the much shorter simplex and indicate the simplex with $d+1$ vertices using the symbol $S(d+1)$ .”

[5] Edmund [Frederick] Robertson, John O’Connor (2023 December) “SIMPLEX”, in MacTutor History of Mathematics Archive: Earliest Known Uses of Some of the Words of Mathematics‎^[1], archived from the original on 2023-12-25.

[6] De Vaan, Michiel (2008) “-sem-, sim-”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 553

[7] De Vaan, Michiel (2008) “-plex”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 473

[1]

[2]

[3]

[4]

[5]

[1]

[2]

simplex

English

Etymology

Pronunciation

Adjective

Derived terms

Related terms

Translations

Noun

Synonyms

Derived terms

Related terms

Translations

References

Further reading

Latin

Etymology

Pronunciation

Adjective

Declension

Derived terms

Related terms

Descendants

References

Further reading

Romanian

Etymology

Noun

Declension