Use of English


A stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron.

The mass of the proton is 1836 times greater than that of the electron. The atoms of each chemical element have a characteristic number of protons in the nucleus; this is known as the atomic number. The common isotope of hydrogen has a nucleus consisting of a single proton.



Any of a number of subatomic particles carrying a fractional electric charge, postulated as building blocks of the hadrons. Quarks have not been directly observed but theoretical predictions based on their existence have been confirmed experimentally.

Quarks have the different states up, down, top, bottom, charm and strange.  Use a space after the state:

Of all the quarks I have studied, I find the up quark the most intriguing.

Unless they are used as compound adjectives:


quark-gluon plasma

Lower case, note the position of the single hyphen.

punctuation, style


A quench is an abnormal termination of magnet operation that happens when part of the superconducting coil goes back to its normal (resistive) state. This can happen if the field inside the magnet is too large, the rate of change of field is too large (causing eddy currents and heating in the copper support matrix), or a combination of the two. More rarely a defect in the magnet can cause a quench. 


quotation marks

Use double quotes in text, captions, etc. Single quotes for headlines, and quotes within quotes. See quotes.

Do not use quotation marks to soften headlines. 

Higgs boson "found" does not mean anything. The quote marks render the headline ambiguous and confuse the reader. Has it been found or not?

CERN physicists spot tantalizing hints of Higgs boson is more elegant and gives more information, without the need for quotes. 

punctuation, style


Readers are entitled to believe that anything appearing within direct quotes are the actual words used by the speaker.

  • Remove ums and aahs and correct for grammar 
  • If you are unsure of the exact wording use reported speech 
  • Open quotes with a colon, and close them after the punctuation mark
  • Use says, not said (though said is permissibile for famous historical examples)

"I really enjoyed the part about the accelerators," says Joe Bloggs. "It got me interested in physics again."

punctuation, style

radiofrequency cavity

No hyphen.

Spell out on first mention, then abbreviate to RF cavity

spelling, style


Use digits separated by a colon; all closed up.





Follow the Harvard referencing system. 

Details here



Think before you use this word. Can you be more specific? What kind of scientist are they? A physicist? A theorist?

Avoid empty phrases such as: Scientists have learned in recent years that... Such a construction doesn't convey any useful information.

See forbidden words



Is preferable to colloquiumWe're writing in English, not Latin.



No hyphen. 

In 2013, the Large Hadron Collider (LHC) will start its first long shutdown for maintenance.

Do not confuse the noun will the phrasal verb:

The research project was shut down due to lack of funding.



The SI unit of dose equivalent (the biological effect of ionizing radiation), equal to an effective dose of a joule of energy per kilogram of recipient mass.

symbol: Sv



Number, no hyphen (except as a compound adjective), lower case "s"

Particle physicists describe the certainty of a result on a scale that goes up to 5 sigma. One sigma could be a random statistical fluctuation in the data, 3 sigma counts as evidence, but only a full 5-sigma result is a discovery. By definition, the probability that a 5-sigma result is wrong is less than one in a million.

1 sigma

3 sigma

5 sigma etc. 

The certainty of the result was given as 3 sigma.

physics, style

sign in

And sign out

Never "Log in, log out".

Note for web developers: This functionality should be handled by the CERN toolbar.



Never use a "smiley" icon in any CERN communication



CERN follows the “British English” rules for spelling, set out in the Oxford English Dictionary.

Check this style guide first for exceptions and points of grammar, then consult the OED.

For guidelines on writing in French – for CERN websites and print documents alike – refer to the translation department's "Guide de Typographie".

spelling, style


Not spokesman or spokeswoman


Standard Model

Caps when referring to the theory of particle physics.

The Standard Model is a theory that describes particle physics. The MacBook is a standard model of computer.

Add a hyphen when using the term as a compound adjective: 

The results of the experiment were consistent with Standard-Model predictions.

Avoid abbreviating Standard Model to SM. It’s irritating to the reader to have to check back on unnecessary abbreviations.

physics, style

strapline ("strap")

Straps are a maximum of 150 characters, including spaces. 

The strap gives added “teaser” information not included in the headline, providing a succinct summary of the most important points of the article. It tells the reader what to expect, and invites them to find out more. 

Remember the strap will always appear with the headline, never on its own, and usually in lists.

Such a list might appear on the site like this (headlines in bold, straps below): 



No hyphen



No hyphen when added as a prefix.

superconductivity, supercomputer, superfluid, etc

The one exception is "super-duper" (informal English meaning "fantastic, wonderful") which should only be used in quotes.



A neutrino detector in Japan. 

Capital S, capital K, hyphen. 

See their website



Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature. 

Superconducting is preferable to "superconductive" as an adjective (though both are technically correct). 

The superconducting wires on the Large Hadron Collider are maintained at 1.9 K (-271.3°C) – colder than outer space – by a closed liquid-helium circuit.


physics, style


Capital "S" when referring to CERN's first particle accelerator. Otherwise, lower case. 

A synchrocyclotron is a type of cyclotron in which the frequency of the driving radiofrequency-electric-field is varied to compensate for relativistic effects as particle velocity approaches the speed of light. This is in contrast to the classical cyclotron, where this frequency is constant.

CERN's first accelerator, the Synchrocyclotron, first started up on 11 May 1957. It was one of the few synchrocyclotrons in the world at the time. 

physics, spelling, style


Not synchro-cyclotron, synchrocyclotron, or other such historical derivations.

A synchrotron is a cyclotron in which the magnetic field strength increases with the energy of the particles to keep their orbital radius constant.

physics, spelling, style


Each piece of content on the CERN website should be tagged with up to five relevant tags.

Tags should be

  • Relevant to the piece of content
  • Lowercase, except for acronyms (many experiments are therefore uppercase) and surnames
  • Do not use Christian names, only surnames, capitalized


ASACUSA, antimatter, Smith, engineering, positron


asacusa, Antimatter, James Smith, engineers, positrons

Use the Taxonomy Manager module on the CERN website to sort out the tags.


tau particle

An unstable subatomic particle of the lepton class, with a charge of −1 and a mass roughly 3500 times that of the electron.



Singular or plural? See collective nouns.

grammar, style

telephone numbers

Telephone numbers should be written in the following format


Where (+XX) is the country code, (YY) the area code, and then the rest (ZZ ZZZ ZZ).

The area code for Geneva is 22 and all CERN telephones start with 76. So most CERN numbers will be in the format

+41 22 76 ZZZ ZZ

CERN internal phone numbers are all five-digit numbers, all reachable directly from CERN.




Lower case. Not Terabyte, or worse, TeraByte

A unit of information equal to one million million (1012) or, strictly, 240 bytes.

There is an estimated one million terabytes of online information, and this amount is growing with every new web page that is posted.

computing, style


The SI-derived unit of magnetic flux density. Though it has a lower-case "t" when spelled out it full, its symbol is an upper-case "T". 


The tesla (T) is the SI-derived unit of magnetic flux density.

physics, style


Not theoretician


Use 2pm, 3.30am (closed up) unless there is a good reason not to.

Note: noon is 12pm, midnight is 12am. It may be clearer to say "noon" or "midnight"

For press releases as well as military, space and similar stories, the 24-hour clock may be more appropriate:

1630 GMT, 1130 Eastern Standard Time

Note: To configure the correct date format on a Drupal site, go to admin/config/regional/date-time/formats/40/edit. 

The PHP code you need to add in the Format string box is "j M Y, g.ia"


time zones

Can be confusing. Your best bet is to use this time zone converter on the "Use a chosen date/time" setting to double-check exact times. 



One word, no hyphen.



Not entitled



Do not use titles such as Mr, Miss, Dr or Professor.

Job titles

Only use one job title for each person. Do not capitalize job titles, unless it is an important government position: Barack Obama, President of the US.

The single exception is CERN Director-General.

Correct uses

"This is a fantastic result for CERN," says ATLAS spokesperson Albert Einstein.

British Foreign Secretary William Hague agreed.



One word.



Means a thousand billion, (the same as one million million) but use with care. House style dictates it may be clearer to say 1012. See numbers.

Use 1015 rather than quadrillion, unless you are deliberately setting out to put dramatic effect ahead of clarity.



Note the "u"

X-rays have been used to treat tumours since 1895.

spelling, style


Capital "T" in text - but note there is a lower-case "t" in the Twitter logo. 


under way

Two words.


All SI units are lower case when spelled out: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), candela (cd), mole (mol).

note: The tesla is the SI-derived unit of magnetic flux density. It has a lower-case "t" when spelled out, though its symbol is an upper-case "T".

Spell them out on first mention, then use the symbol.

I weigh 75 kilograms. Last month I gained 4 kg after I stopped runnning 5 kilometres every morning.



Always lower case


Where it is useful to advertise a URL (in printed materials, for instance) use the following format:[sitename]

Example: (note that this resolves to, which is less easy for new users to remember).


  1. Use lowercase characters
  2. Omit the 'http://' or 'https://' unless it is necessary

It may seem obvious, but check that the URL is relevant, and always double-check links are working before publishing. See also: links.



Not USA. There is hardly every any need to spell out United States, even at first mention. America is preferable in some contexts (“God bless the US” would sound silly).  It is permissible to use "American" instead of "US" as an adjective.



But vaporize



In particle physics, an interaction point (IP) is the place where particles collide. One differentiates between the nominal IP, which is the design position of the IP, and the real or physics IP, which is the position where the particles actually collide. The real IP is the primary "vertex" of the particle collision.



Don't use it – it's usually redundant. Just think of a better word. Not “very big”, but huge, vast, etc. Not "very small" but tiny, minute, etc.

The exceptions are when "very" is used to mean "actual; precise" as in those were his very words, or to mean "without addition; mere" as in the very thought made her shudder. Those uses are fine.

See forbidden words.

grammar, style


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