Definition of "Janus"

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 Domestic war now rendered the admonition superfluous, and the ceremony was superseded by the establishment of a new religion. But the brazen temple of Janus was left standing in the forum; of a size sufficient only to contain the statue of the god, five cubits in height, of a human form, but with two faces, directed to the east and west.

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; republished Philadelphia, Pa.: Published by William Y. Birch & Abraham Small, No. 37, South Second Street; printed by Robert Carr, 1805, OCLC 15453273, page 166

[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 temper: with this view, he built a temple to Janus, near the foot of the hill Argiletum, which was to notify a ſtate either of war or of peace: when open, it denoted that the ſtate was engaged in war; when ſhut, that there was peace with all the ſurrounding nations.

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 Mr. Cadell) in the Strand, book I, page 35

"I'll tell you what we can do," cried her persevering patroness; "we can go as masks, and Lady Juliana shall know nothing about it. That will save the scandal of an open revolt or a tiresome dispute. Half the company will be masked; so, if you keep your own secret, nobody will find it out. Come, what characters shall we choose?" / "That of Janus, I think, would be the most suitable for me," said Mary.

1810, anonymous [Susan Edmonstone Ferrier], “chapter XVI”, in Marriage, a Novel. In Three Volumes, volume II, Edinburgh: William Blackwood, Prince's-Street: and John Murray, Albemarle-Street, London, published 1818, page 218

We find ourselves once again sitting in Committee of the Whole House to vote a war subsidy. The present occupants of the Treasury Bench are determined that so long as they retain their places the Temple of Janus shall not be closed.

1879 February 27, A[lexander] M[artin] Sullivan, “On the Zulu War” (speech before the House of Commons of the United Kingdom); quoted in William Jennings Bryan, editor, Irish Orations (The World's Famous Orations), volume VI, New York, N.Y.: Funk & Wagnalls, 1906, OCLC 23127203, and republished on Bartleby.com, 2002, archived from the original on 4 October 2015

Janus, with his two heads, his mystery, his depiction as both laughing and serious, and the obvious parallel this forms with the masks of attic tragedy and comedy would make him a double of the two-headed man, the conjurer, and an associate of the trickster in folk comedy as well.

2008, John Lowe, “Laughin’ up a World: Their Eyes Were Watching God and the (Wo)Man of Words”, in Harold Bloom, editor, Interpretations: Zora Neale Hurston’s Their Eyes Were Watching God (Bloom’s Modern Critical Interpretations), new edition, New York, N.Y.: Bloom's Literary Criticism, Infobase Publishing, page 75

Good reviews look both backward and forward; an argument could even be made that one must look backward in order to discern the way forward, that backward and forward are two sides of the same research coin. Nowhere is such a Janus-like perspective more apparent than in the current set of reviews.

2011, Robert M. Hodapp, “Preface”, in Robert M. Hodapp, editor, International Review of Research in Developmental Disabilities, volume 41, San Diego, Calif.: Academic Press, page xi

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 of poetry parallels in a polysemous manner both the line that precedes it and the line which follows it.

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 Press, page 12

The novel seems to be rather autobiographical, but in retrospect one can see about three-quarters through the text there is a turn from an autobiographical into a future novel […]. De chauffeur verveelt zich is a real Janus-novel, looking into two directions.

2004, Ad Zuiderent, “The Historical Pole of the Earth: Time in the Novels of Gerrit Krol”, in Thomas F[rederic] Shannon, Johan P[ieter] Snapper, editors, Janus at the Millennium: Perspectives on Time in the Culture of the Netherlands (Publications of the American Association for Netherlandic Studies; 15), Lanham, Md.: University Press of America, page 93

The ability to look at both sides of a coin before giving a verdict can be both a curse and a blessing. […] This "Janus effect" (my term) is a curse when it blocks a time sensitive judgment response, or a decision waiting to be made before long. […] Friendships, sibling harmony, good relationship with associates at work, and especially marriages, could be great and positive recipients of the good that such a Janus effect could bring on.

2012, Ruby L. Agnir, “Janus”, in Upward beyond the Brim: Transcending the Limits: Selected Writings, [Bloomington, Ind.]: Xlibris

A Janus fluid is one made of Janus particles immersed in a solvent. A Janus particle like the Roman God Janus, […] is one that has two faces with two different functionalities.

2013, Riccardo Fantoni, “What is a Janus Fluid?”, in The Janus Fluid: A Theoretical Perspective (Springer Briefs in Physics), Cham, Switzerland: Springer, page 1

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, title page

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, 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 116 km in diameter.

2016, Michael [W.] Carroll, “Ice Dwarfs and Tiny Moons”, in Picture This!: Grasping the Dimensions of Time and Space, Cham, Switzerland: Springer Nature, page 56