American and British English spelling differences

Different spellings, different connotations

• dependant or dependent: British dictionaries distinguish between dependent (adjective) and dependant (noun). In the US, dependent is usual for both noun and adjective, notwithstanding that dependant is also an acceptable variant for the noun form in the US.^[101]
• disc or disk: Traditionally, disc used to be British and disk American. Both spellings are etymologically sound (Greek diskos, Latin discus), although disk is earlier. In computing, disc is used for optical discs (e.g. a CD, Compact Disc; DVD, Digital Versatile/Video Disc), by choice of the group that coined and trademarked the name Compact Disc, while disk is used for products using magnetic storage (e.g. hard disks or floppy disks, also known as diskettes).^[102] For this limited application, these spellings are used in both the US and the Commonwealth. Solid-state devices also use the spelling "disk".
• enquiry or inquiry:^[103] According to Fowler, inquiry should be used in relation to a formal inquest, and enquiry to the act of questioning. Many (though not all) British writers maintain this distinction; the OED, on the other hand, lists inquiry and enquiry as equal alternatives, in that order. Some British dictionaries, such as Chambers 21st Century Dictionary^[104], present the two spellings as interchangeable variants in the general sense, but prefer inquiry for the "formal inquest" sense. In the US, only inquiry is commonly used. In Australia, inquiry and enquiry are often interchangeable, but inquiry prevails in writing. Both are current in Canada, where enquiry is often associated with scholarly or intellectual research.
• ensure or insure: In the UK (and Australia), the word ensure (to make sure, to make certain) has a distinct meaning from the word insure (often followed by against – to guarantee or protect against, typically by means of an "insurance policy"). The distinction is only about a century old^[105], and this helps explain why in (North) America ensure is just a variant of insure, more often than not. According to Merriam-Webster's usage notes, ensure and insure "are interchangeable in many contexts where they indicate the making certain or [making] inevitable of an outcome, but ensure may imply a virtual guarantee ensured the safety of the refugees>, while insure sometimes stresses the taking of necessary measures beforehand insure the success of the party>.^[106]
• insurance or assurance: In the business of risk transfer, American English speakers will normally refer to life insurance or fire insurance, whereas historically British English speakers would more commonly refer to life assurance, reserving insurance for the home. This distinction no longer applies, with British companies as likely as US ones to provide "life insurance". Canadian speakers remain more likely than US speakers to use assurance.^[107]
• matt or matte: In the UK, matt refers to a non-glossy surface, and matte to the motion-picture technique; in the US, matte covers both.^[108]
• programme or program: The British programme is a 19th-century French version of program. Program first appeared in Scotland in the 17th century and is the only spelling found in the US. The OED entry, written around 1908 and listing both spellings, said program was preferable, since it conformed to the usual representation of the Greek as in anagram, diagram, telegram etc. In British English, program is the common spelling for computer programs, but for other meanings programme is used. In Australia, program has been endorsed by government writing standards for all senses since the 1960s^[109], although programme is also seen; see also the name of The Micallef Program(me). In Canada, program prevails, and the Canadian Oxford Dictionary makes no meaning-based distinction between it and programme. However, some Canadian government documents nevertheless use programme in all senses of the word – and also to match the spelling of the French equivalent.^[109]
• tonne or ton: in the UK, Australia, Canada and New Zealand, the spelling tonne refers to the metric unit (1000 kilograms), whereas in the US the same unit is referred to as a metric ton. The unqualified ton usually refers to the long ton (2,240 lb.) in the UK (but note that the tonne and long ton differ by only 1.6%, and are roughly interchangeable when accuracy is not critical; ton and tonne are usually pronounced the same in speech), and to the short ton (2,000 pounds (910 kg)) in the US.

See also meter/metre, for which there is a British English distinction between these etymologically related forms with different meanings but the standardised American spelling is "meter". The spelling used by the International Bureau of Weights and Measures is "metre".^[110] This spelling is also the usual one in most English-speaking countries, but only the spelling "meter" is used in American English, and this is officially endorsed by the United States.^[111]

A few British publications prefer to use kilogramme for the metric unit of mass and gramme, but kilogram and gram are the more common spellings in British English and therefore listed first in British dictionaries. In the United States, the spellings are always (kilo)gram, and these are also used exclusively by the International Bureau of Weights and Measures.

Telegramme is used in some places, but never in the United States, where it was always telegram.