I'd never ask such a question as I thought clarity is the top issue the rest is margin. If you can't think straight, you can't write straight - you confuse your readers.
Grammar is nothing compared with your ideas. if you have an idea, you can write well. If you don't have ideas, you can't write well no matter how good you get your grammar right.
So, the take home message is that sharpen your thought before you write. That's why I ask you to throw away your grammar books out of window. Grammar books help you take exams, not write.
You can't be writing like Hemingway without clarity in your head. Writing like Hemingway is not his style of writing concise, short sentences, short paragraphs, but his clarity of mind.
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How short is short? Recommended average number of words per sentence
Plain English books, articles, and guides tell us to keep our sentences short. I like what Steven D. Stark said: “The more complicated your information is, the shorter your sentences should be.” I also like what Rachel McAlpine said: “If you want your English to be understood worldwide—write short sentences.” But how short is short?
[1] For legal writing, the average number of words per sentence as recommended by Plain English authorities and government offices:
15 words (Federal Register Document Drafting Handbook, October 1998 Revision, page 216)
Between 15 and 18 (“Plain English: Eschew Legalese” by Judge Gerald Lebovits, New York State Bar Association Journal, November/December 2008, page 60)
18 words (“Appellate Practice—Including Legal Writing From A Judge’s Perspective”, page 7, by Judge Mark P. Painter, the only American so far to be appointed to the UN Appellate Tribunal)
20 words or fewer (US Federal Aviation Administration “Writing Standards, Order 1000.36”)
20 words (“Legal Writing in Plain English” by Bryan A. Garner)
20 words (“How to write clearly” from European Commission)
20 to 25 words (“How to create clear announcements” Project on the Use of Plain Language, by Hong Kong Securities and Futures Commission”)
20 to 25 words (“Tips for Better Writing in Law Reviews and Other Journals” by Joseph Kimble, Michigan Bar Journal, October 2012)
22 words (“Just Writing: Grammar, Punctuation, and Style for the Legal Writer” by Anne Enquist and Laurel Currie Oates)
25 words (“Mightier Than the Sword: Powerful Writing in the Legal Profession” by C. Edward Good
continued
James Quinn
Beware of averages. There should be a rythym of long and short sentences that establishes s meter for the piece.
Christina Zarcadoolas
To add my penny here - there's a world of difference in readability load between a long sentence that is strung together by simple compounds ( she ate a frankfurter and then ate french fries and a coke, and then.....) and one made up of multipli-embedded phrases and clauses ( the dog, who was chasing the cat stopped when the boy, who was crossing the street, climbed into a tree that contained a beehive, whined ( who wined). And to use Chomsky's classic example - short ain't necessarily a sure bet either. "Flying planes can be dangerous".
Gerry Galacio
Plain Language guidelines do not simply recommend that sentences should be short. Rather, the guidelines say that sentences should be short and clear. (Clarity oftentimes results from brevity.)
But perhaps, the guideline should not be to make our sentences short and clear.
Joseph M. Williams and George Gopen have been teaching since the 1990s about sentence structure (topic and stress positions). Perhaps then, the right guideline should be to make our sentences short, clear, and strong.
Rosalind Moffitt
I agree Josiah, providing accessible information is not about 'spinning a good yarn'. I also agree there is art in writing, but to adapt information also requires technical knowledge, such as Christina mentions. What can be lacking in a discussion about ideal sentence length is mention of the reader/ recipient. Readers' language, cognitive and information needs should inform all decisions about how information is structured and delivered. This is even more important when readers have low literacy or disabilities. Understanding written information requires processing at multiple levels. To make information accessible we need to address all the factors that contribute to difficulty. Short sentences can increase difficulty for some readers, therefore advice to use 'short' sentences can be unhelpful.
Christina Zarcadoolas
A factor not yet mentioned, and one that relates to Rosalind's comment about the reader perspective is line length, not sentence length. I've found that actual physical line length on a page plays an important role with less able readers. I'm always amazed when I see a website that uses full screen length to present print.
Josiah Fisk
These are all great points. It really underlines how there are so many factors that affect a communication's ability to engage target readers/users and to deliver information in a way they can comprehend it.
It's good to know about the factors that tend to have a degree of universality (such as sentence length, line length, and structure), but I believe it's just as important to bear in mind that so many of the factors in any given case are NOT universal -- they are very specific.
I'd say it's also important to distinguish between factors that are relatively simple and easily addressed (line length) and those such as structure that can take years to fully understand and master.
Chacko P.G.
Very informative, Gerry. Indisputably, easily comprehensible expression of ideas, however complex, in short sentences without jargons is an art that belongs to one who has mastery of one's language.
Gregory Cuppan
I am wading in late here in an interesting discussion that ties into part of my work world of optimizing patient informed consent documents. We continually look at how sentence length, line length, paragraph size, and sequencing of topics impact readability and comprehensibility.
Readability and comprehensibility of a given text depends upon the kind and number of ideas the text expresses and the vocabulary required to express those ideas. The reading research also suggests style, format and typography will impact these factors as well. The net-net is sentence length guidance is influenced by the medium used to present the information, complexity of topic, vocabulary load, and audience skills and interest.
Atul Pande
How about trying to write so the only punctuation is at the end of a sentence? Try it sometime. It's amazing how clearly you can express your ideas.
Gregory Cuppan
Hey Atul......this is excellent advice. I recall often your great comment to me about "writing like Hemingway."