• (noun) IPA: /ˈɹiːflɛks/
• (verb) IPA: /ɹɪˈflɛks/

reflex (plural reflexes)

1. An automatic response to a simple stimulus which does not require mental processing.
   • 1970, Stanisław Lem, trans. Joanna Kilmartin and Steve Cox, Solaris (novel):

     For a while, I shall have to make a conscious effort to smile, nod, stand and perform the thousands of little gestures which constitute life on Earth, and then those gestures will become reflexes again.

2. (linguistics) The descendant of an earlier language element, such as a word or phoneme, in a daughter language.
3. The descendant of anything from an earlier time, such as a cultural myth.

   • The superstition of the loup-garou, or werewolf, belongs to the folklore of most modern nations, and has its reflex in the story of "Little Red Riding-hood" and others.

4. (mostly, photography) Reflection or an image produced by reflection. The light reflected from an illuminated surface to one in shade.

   A reflex camera uses a mirror to reflect the image onto a ground-glass viewfinder.

   • c. 1591–1595, William Shakespeare, “The Tragedie of Romeo and Ivliet”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies (First Folio), London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, OCLC 606515358 ↗, [Act III, scene v]:

     Yon gray is not the morning's eye, / 'Tis but the pale reflex of Cynthia's brow.

5. 1849, [Alfred, Lord Tennyson], In Memoriam, London: Edward Moxon, […], published 1850, OCLC 3968433 ↗, (please specify ):

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   On the depths of death there swims / The reflex of a human face.

• French: réflexe
• German: Reflex
• Italian: riflesso
• Portuguese: reflexo
• Russian: рефле́кс
• Spanish: reflejo

• French: continuateur
• German: Kontinuante, Fortsetzer
• Italian: riflesso, continuatore
• Spanish: reflejo, continuador

reflex

1. Bent, turned back or reflected.

   • the reflex act of the soul, or the turning of the intellectual eye inward upon its own actions

2. Produced automatically by a stimulus.
3. (geometry, of an angle) Having greater than 180 degrees but less than 360 degrees.
   • 1878, James Maurice Wilson, Elementary Geometry, MacMillan, page 10 ↗:

     A polygon is said to be convex when no one of its angles is reflex.

   • 1895, David Eugen Smith and Wooster Woodruff Bernan, New Plane and Solid Geometry, page 7:

     An angle less than a right angle is said to be acute; one greater than a right angle but less than a straight angle is said to be obtuse; one greater than a straight angle but less than a perigon is said to be reflex or convex.

   • 1958, Howard Fehr, “On Teaching Dihedral Angle and Steradian” in The Mathematics Teacher, v 51, National Council of Teachers of Mathematics, page 275:

     If the reflex region is the interior of the angle, the dihedral angle is reflex.

   • 1991, B. Falcidieno et al, “Configurable Representations in Feature-based Modelling” in Eurographics '91: Proceedings, North-Holland, page 145:

     A reflex edge of a polyhedron is an edge where the inner dihedral angle subtended by two incident faces is greater than 180°.

   • 2001, Esther M. Arkin et al, “On the Reflexivity of Point Sets”, in Algorithms and data structures: 7th International Workshop, WADS 2001: Proceedings, Springer, page 195:

     We say that an angle is convex if it is not reflex.

   • 2004, Ana Paula Tomás and António Leslie Bajuelos, “Quadratic-Time Linear-Space Algorithms Generating Orthogonal Polygons with a Given Number of Vertices”, in Computational Science and Its Applications – ICCSA 2004 Proceedings, part 3, Springer, page 117:

     P denotes a polygon and r the number of reflex vertices.

4. (painting) Illuminated by light reflected from another part of the same picture.

• (of an angle) re-entrant

reflex (reflexes, present participle reflexing; past and past participle reflexed)

1. (transitive) To bend, turn back or reflect.
2. To respond to a stimulus.