Janus

Proper noun

Janus

1. (Roman) The god of doorways, gates and transitions, and of beginnings and endings, having two faces looking in opposite directions.
   • In the ages of victory, as often as the senate decreed some distant conquest, the consul denounced hostilities, by unbarring, in solemn pomp, the gates of the temple of Janus. Domestic war now rendered the admonition superfluous, and the ceremony was superseded by the establishment of a new...1789, Edward Gibbon, chapter XLI, in The History of the Decline and Fall of the Roman Empire, volume V, London: Printed for A[ndrew] Strahan, and T[homas] Cadell, in the Strand, OCLC 30106274...
   • [K]nowing that the minds of the people, rendered ferocious by a military life, would never accommodate themſelves to the practice of theſe [principles of justice, laws, and morals], during the continuance of war, he [Numa Pompilius] reſolved, by a diſuſe of arms, to mollify the fierceneſs of their...1797, Titus Livius [Livy], translated by George Baker, The History of Rome, [...] In Six Volumes, volume I, London: Printed for A[ndrew] Strahan, and T[homas] Cadell Jun. and W. Davies (successor to...
2. (attributive) Used to indicate things with two faces (such as animals with diprosopus) or aspects; or made of two different materials; or having a two-way action.
   • Janus cat, Janus particle
   • But other categories of word-play have not been researched extensively or systematically. Among the latter is the type of word-play known as polysemous parallelism, or more commonly, Janus parallelism. The latter term was coined by Cyrus Gordon to describe a literary device in which a middle stich...1996, Scott B. Noegel, “Introduction to Janus Parallelism”, in Janus Parallelism in the Book of Job (Journal for the Study of the Old Testament Supplement Series; 223), Sheffield: Sheffield Academic...
   1. (attributive) Used to indicate an azo dye with a quaternary ammonium group, frequently with the diazo component being safranine.
      • Janus green B is a dye used widely in histology to stain cells for microscopic examination.
      • In order to show that such stains are due to oxycellulose, the fabric should be stripped with titanous chloride solution or sodium hydrosulphite. On redyeing with Janus Blue the oxycellulose patches are more heavily dyed. The writer prefers Janus Blue to the Methylene Blue which is usually...1921, Textile Colorist, volume 43, New York, N.Y.: Howes Publishing Company, →ISSN, →OCLC, page 401
3. (figuratively) A two-faced person, a hypocrite.
   • The hypocrite; or, The modern Janus.1814, Selina Davenport, The Hypocrite; or, The Modern Janus. A Novel. In Five Volumes, volume I, London: Printed at the Minerva-Press, for A. K. Newman and Co. Leadenhall-Street, →OCLC, title page
4. A moon of Saturn.
   • Heavily cratered and irregularly shaped, Janus orbits Saturn just beyond the F ring and only 50km (30 miles) farther away than its co-orbital moon, Epimetheus.2012 October, “Saturn”, in Martin Rees, editor, Universe, rev. edition, London: Dorling Kindersley, →ISBN, page 192
   • Two of Saturn's small moons have the unique distinction of sharing the same orbit. Epimetheus and Janus circle the Lord of the Rings at a distance of just over 151,000 km, about half the distance from Earth to the Moon. Both are irregularly shaped. Janus is 179 km across, while Epimetheus is about...2016, Michael [W.] Carroll, “Ice Dwarfs and Tiny Moons”, in Picture This!: Grasping the Dimensions of Time and Space, Cham, Switzerland: Springer Nature, →DOI, →ISBN, page 56
5. (rare) A male given name from Latin.