Hyphens - Proposed new version


We discuss here the general principles and CMS style recommendations governing hyphens.

Hyphens should be used to increase clarity, but there is no universally accepted set of hyphenation rules. The trend in scientific writing is to avoid a hyphen when it does not serve a useful purpose, e.g. "pileup", "cross section", "b quark". The recommendations given here are intended for guidance. Authors should feel free to include or omit a hyphen to improve the clarity in any situation, regardless of any rules. Authors should also keep in mind that reorganizing a sentence may be a better way to resolve ambiguities than adding a hyphen.

Hyphenation conventions for commonly used or troublesome terms

Two or more words, unhyphenated

b jet beam halo particles heavy ions jet energy corrections standard model $x$ axis
b quark black hole heavy ion collisions jet energy scale standard model predictions Z boson
b quark jet black hole models Higgs boson $K$ factor tau lepton Z boson production
b tag colour singlet state Higgs boson mass lead tungstate top quark decays  
b tagging cross section in the $t$ channel Monte Carlo W boson  
b tagging efficiency cross section measurement invariant mass distribution single top quark production W boson candidate  

A single word without a hyphen

anticlockwise dimuon noncollinear nonprompt preselection subchannel
antiquark electroweak noncollision nonrelativistic preshower subdetector
buildup endcap nondiffractive nonresonant pseudorapidity subleading
counterclockwise misidentified nonflow nonuniform pseudoscalar subprocess
cutoff misreconstructed nonisolated nonvanishing readout subsample
diboson mistagging nonlinear nonzero reweighted  
dilepton monojet nonnegligible pickup semileptonic  
dijets multijet nonperturbative pileup standalone  


anti-\kt algorithm data-taking period hard-scattered partons multiple-parton interactions short-range correlations
b-tagged jet double-muon trigger high-\pt jets next-to-leading-order calculation signal-to-background ratio
beam-gas events event-by-event fluctuations initial-state radiation particle-flow algorithm $t$-channel processes
bin-by-bin correction final-state radiation least-squares fit phase-space region two-dimensional histogram
calculated to next-to-leading order fourth-generation quarks matrix-element generator proton-proton collisions $x$-$y$ plane
centre-of-mass energy four-momentum maximum-likelihood fit pseudo-experiments  
charged-hadron multiplicity gas-ionization detector minimum-bias event quark-gluon scattering  
charged-pion mass global-muon trigger minimum-ionizing particle root-mean-square  

Use a hyphen
The following should be hyphenated as attributive adjectives. (An attributive adjective is an adjective that comes before the noun that it is describing or qualifying.)

  • A noun + present or past participle: "gas-filled chambers", "English-speaking people", "U-shaped tube".
    Some combinations form passive verb forms, so they must be hyphenated to show they are performing as a unit, e.g. "Doppler-shifted", "Fourier-transformed".

  • An adjective + present or past participle: "good-sized sample", "straight-sided cavern", "fine-grained texture"

  • "Well", "ill", or "little" + past participle: "well-known theorem", "ill-defined terms", "little-known result".
    Do not hyphenate if the adjective is modified by an adverb: "very well known theorem", "extremely fine grained texture".

  • A preposition + noun or adjective: "near-surface reaction", "near-death experience", "next-to-leading-order calculation" (but "calculated to next-to-leading order")

  • Temporary compounds formed by an adjective + noun indicating number, dimension, or quality: "single-photon approximation", "three-component gas", "nth-order equation", "low-\pt region".
If a combination that would normally require a hyphen is modified by an adverb, a hyphen is not used: "high-\pt particles", but "very high \pt particles".

Do NOT use a hyphen
The following combinations should NOT be hyphenated as attributive adjectives.

  • An irregular comparative or superlative + participle or noun: "best known result", "least known theorem"

  • Foreign phrases: "a priori solution", "in situ technique"

  • Adverbs ending in "ly" + adjective or participle: "slowly flowing gas", "highly complex approach", "oppositely charged particles"

  • Chemical compounds: "sulfuric acid bath", "carbon dioxide gas", "lead tungstate crystals"

  • Compounds indicating direction or placement: "upper right corner", "north central Switzerland"

  • Temporary compounds used as attributive adjectives formed by a noun + noun: "energy flow region", "wake surface potential", "jet energy corrections"

  • Permanent compounds (frequently used word combinations) that have their own (unhyphenated) dictionary entries: "Higgs boson", "Z boson", "W boson", "top quark", "cross section", "standard model", "black hole", "cosmic ray", "magnetic field", "form factor"

  • Other combinations of an adjective + noun that may be considered permanent because of their common usage in our field: "b quark", "b tagging", $\tau$ lepton, "$t$ channel", "$S$ wave"

  • Comparative modifiers using "more" or "less" do not need hyphens except on the rare occasions when the meaning is ambiguous without one. For example, "the well read paper", "the less known algorithm".

Usually use a hyphen
The following category of attributive adjectives usually take a hyphen, but some recommendations or journal guidelines will differ.

  • Phrases that act as attributive modifiers: "signal-to-noise ratio", "order-of-magnitude estimate", "tag-and-probe procedure"

Always use a hyphen

  • Phrases that are listed in the dictionary with hyphens should always use them: "day-to-day variation", "one-to-one correspondence"


  • Do not hyphenate a noun + gerund or fractions when they act as nouns in a sentence: "problem solving", "data taking", "one half", "two thirds". But do hyphenate them when they are used as an adjective, e.g. "data-taking period", "two-thirds full".

  • Use a hyphen with "self" compounds and a verb + preposition (acting as a noun): "self-destruct", "turn-on", "ramp-up"

Words of equal weight
A hyphen is used to connect words of equal weight. Usually, they are connected because they have an "either-or", "from-to", or "between-and" relationship: "wave-particle duality", "argon-ethane gas", "time-space plot", "May-December relationship".

PACS keywords
When specifying the PACS keywords associated with a paper, hyphenate them as they appear in the official listings.

En dashes and em dashes
Use an en dash (a double hyphen -- in LaTeX, with no spaces) to indicate a range of values, e.g. "5--10", or something attributed to two people, e.g. "Bose--Einstein correlations". Use an em dash (a triple hyphen --- in LaTeX, with no spaces) for an article of punctuation, e.g. "The measurement failed---we messed it up."

Two related hyphenated words near each other
If you have two related hyphenated words near each other in a sentence, you can shorten the first hyphenated word by omitting the hyphenated part and leaving a hyphen at the end of it. Example: "Both initial- and final-state radiation are taken into account."

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Topic revision: r14 - 2014-10-17 - StevenWasserbaech
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