Entries - F


A unit of area, equal to 10−43 square metres. See barn and inverse femtobarn.

"Femto" means a factor of 10-15, a thousandth of a millionth of a millionth. So a femtobarn is a barn (10-28 square metres) multiplied by 10-15, which equals 10-43 square metres.

When writing pages for the general public, always give an approximate number of collisions as well as the figure in inverse femtobarns.



Is preferable to "Fermi National Accelerator Laboratory". Link to their homepage.

A new experiment at Fermilab in the US could change our ideas about fundamenal particles.



A subatomic particle, such as a nucleon, which has half-integral spin and follows a statistical description given by Fermi and Dirac.


fewer or less?

For things you can count off one by one, use fewer; for quantities you can only measure, not count, use less.

There were fewer cars on the roads in the 50s.

Fewer people attended the gig than were expected.

I drink less water than you.

John ate fewer apples than Jane.


fire brigade

Or fire service. Lower case.



Not fireman



One s.



Don't use them. 

Except in press releases, where the following footnote should be inserted, linked to the first mention (and only the first mention) of the word "CERN" in the main text.

Note: This version came into force on 14 January 2014. It should be updated if and when any new nations join CERN as member states.



forbidden words

The following is a list of the web editor's pet peeves. It is intended to make writers think more about simple use of English, and for editors to cut jargon where possible.

Don't use the following words or constructions, except in direct quotes.

Access (as a verb)

And/or (Logic gates do not belong in prose)

Anomalous – results are not anomalous, they are “unexpected”



Colloquium – say "seminar" 

grammar, style

foreign and adopted words

Foreign words should be in italic. Where a word has passed into common English usage use roman: be guided by ODE. So Schadenfreude is in roman, because that’s the way it is in the dictionary, while Schaden or Freude (should you ever need to use them) are in italic.




Don't use them. Use decimals instead: 0.25 not 1/4


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

grammar, punctuation, spelling, style

fundamental particle

Is preferred to "elementary particle". There is nothing elementary about the complex interactions of subatomic particles.



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