Spelling mistakes, as we know, are all too common in written English, a language with few rules and abundant oddities. Even native speakers often fall into the trap of mixing their '-ics' with their '-als'. But you don't want to be misunderstood. This essential guide highlights the most common areas of confusion.

There are four, or rather eight, very commonly used words which often get in a muddle. Retain these and you are on the road to crystal clarity...

1. Economic(al)
   There is some small overlap between these two words. However, perfectionists will still prefer to make the distinction clear. Essentially, 'economic' is the adjective related to the field of economics, as in the example "the meeting will concentrate on the economic issues surrounding the project", whereas 'economical' refers more generally to an economy, i.e. a saving to be made, e.g. "travelling by bus is more economical than taking the car".
    
2. Historic(al)
   The difference between these two words is one of neutrality.
   A historic event is one that was of great importance in history and is most likely well-known. An historical event is quite simply an event that took place during the course of history. The first therefore places a value judgement on the event being described. (Note the change in the use of 'a' and 'an' before these two words!).
    
3. Comic(al)
   Both of these words fundamentally refer to something that is humorous and intended to make you laugh, but you should be careful when using comical, as it often has the added meaning of something that is ludicrous or unintentionally funny. Comic, on the other hand, retains its direct link with the idea of comedy, e.g. he "recited a comic poem". Don't forget that a comic, the noun, is the same as a comedian and that "comical behaviour", for example, can also mean that someone is acting oddly.
    
4. Classic(al)
   These two words have many meanings, which are often very similar. However, there are two main areas in which their particular connotations should be observed. Classic is used to refer to items of the highest quality and which are outstanding in their category, such as "a classic children's novel" or again "classic management styles". Classical, on the other hand, is used first and foremost to describe literature, art etc. in the style of ancient Greece or Rome, or for the particular style of music going by this name.
   

Other cases exist, such as with rhetoric and rhetorical, where the former does not exist as an adjective, rather is a noun used to describe a style of language. Chronical is another word that does not exist, the correct form being chronic (although the adverb is spelled chronically). And just to add to the confusion, a chronicle, the noun, is a chronological historical record. Of course, there are a few examples of complete interchangeability; the most obvious one that springs to mind is strategic(al), where both mean the same thing. The best advice is if in doubt, don't hesitate to check in a good dictionary.

By way of an extra note, although this doesn't follow the same thread as the rest of the article, don't forget always to check your spelling of principle and principal - do you know which is the noun?