As stated on p. xii we have used British English spelling except where examples were originally written in American English. This appendix lists words from our text that are commonly spelled differently in these two versions of English, plus a few other important words. The spelling in one may or may not be acceptable in the other. For instance, acknowledgement is usually spelled with an ‘e’ after the ‘g’ in British English but without the ‘e’ in American English (acknowledgment), but both spellings are acceptable in both languages. Judgement and judgment are likewise spelled differently but judgement (with an ‘e’) is not an accepted alternative in American English (see also p. 39).

Sometimes a spelling listed in one language version is used for another purpose in the other. For example, British English demands analogue; the American dictionary Merriam-Webster OnLine lists analogue for the noun, but spells the adjective analog.

Spelling differences sometimes indicate more complex differences in usage: the adjectival endings ‘ic’ or ‘ical’ are cases in point. They can be interchangeable – for instance, the adjectives histopathologic and histopathological are listed in the Merriam-Webster OnLine – but not necessarily consistent: only pathological is listed. The COD has only histopathological, and has pathological, US also pathologic. One of the versions of a word may be more common in British or American English, or can be more common with a particular noun: electrical cord is seen more often than electric cord and electric eel more often than electrical eel. Some adjectives have different meanings in their ‘ic’ and ‘ical’ versions: economic (COD) relates primarily to the economy and secondarily to being good value; so whereas an economic enterprise may be either a gathering of economists or a project that doesn’t cost too much, an economical procedure is one that costs less (see HISTORIC, HISTORICAL).