What are the rules in English language to split words at the end of a line?
Where exactly must the hyphen split the word?
The easiest thing to do, and the only way of being sure you agree with the authorities, is to look words up in the dictionary. Some of the hyphenations currently in American dictionaries make no sense at all. For example, the reason that prai-rie and fair-y are hyphenated the way they are seems to be that 150 years ago, the editors of Webster's dictionary thought they didn't rhyme1; prairie was pronounced pray-ree with a long 'a', while fairy was pronounced fair-ee with an r-colored 'a'.
That said, there are a few hyphenation rules that will let you hyphenate 90% of English words properly (and your hyphenations of the remaining 10% will be perfectly reasonable, even if they disagree with the authorities'). Here they are, in roughly decreasing order of priority:
Finally, if the above rules leave more than one acceptable break between syllables, use the Maximal Onset Principle:
There are lots of exceptions to these rules:
Sometimes the rules conflict with each other. For example, ra-tio-nal gets hyphenated after a short vowel in an accented syllable because ti acts as a digraph indicating that the 't' should be pronounced 'sh'.
Sometimes it's not clear what constitutes a morpheme boundary: why ger-mi-nate and not germ-i-nate?
Sometimes the pronunciation of a word varies—/væpɪd/ or /veɪpɪd/? Merriam-Webster and American Heritage dictionaries agree that both pronunciations are valid, but they disagree about the hyphenation.
And some hyphenations I can't figure out the reason for: the Maximum Onset Principle would suggest pa-stry, but the authorities all agree on pas-try.
1I believe some American dialects still make this distinction in pronunciation; the editors of Webster's dictionary weren't imagining things.
Vincent McNabb gives good advice generally on when to hyphenate—never if you can get away with it, and if you must, in a sensible place.
However, the question of where to hyphenate is something that dictionaries have answered for generations. Every entry has a word split into syllables, and technically speaking, according to traditional rules of typesetting, you can hyphenate a word at any syllable boundary. For example in the Merriam-Webster's online dictionary, the entry for "dictionary" reads "dic·tio·nary"—so you could hyphenate anywhere there appears a centered dot. Of course there are various rules of thumb and heuristics to choose the best place to hyphenate, and in many cases hyphenating a word dramatically reduces readability, but in a strict answer to OP's original question, it is acceptable to hyphenate a word at any syllable boundary, and you can find all the syllable boundaries in a dictionary.
Technically speaking, hyphens are acceptable between any two syllables. But it is best to use them between prefixes, roots, and suffixes if at all. In most casual documents, hyphens decrease readability and oftentimes make documents look more cluttered, despite the fact that they form a nice, neat block. However, in news articles or novels, in places where moving the entire word would compromise the shape of the document, it is very common to see end hyphenation. Pick up a copy of 'Frankenstein' or 'The Magician's Nephew' and I assure you that you'll find quite a few. My copy of 'Seabiscuit' splits tomorrow between pages.
Firstly, it is preferable not to split a word at the end of a line.
From the APA Style Guide, Section 1.A.9
Do not hyphenate (split) words at the end of a line.
If possible, add another word to the line, or take one away, so you don't need to split in the first place.
In fact. NEVER EVER split words. However, I will give what I consider to be ok guidelines:
There are really no proper rules as to how it should be done, when it is, so basically, use common sense. If it must be done, try to keep the components of meaning together - this is easy with obviously compound words, such as keyboard. E.g.
It is also easy with words with prefixes such as "quasi" or "psuedo" e.g.
But mostly, splitting the words just makes them hard to read - and can lead to nightmares when the content of text is changed, because words that were once at the end of a line will no longer be at the end of a line, and everything will have to be re-done.
Unfortunately, most word processors are not very good at automatically splitting words, so it is best to keep that feature off. It is also possible, however, to put markers in words where the word processor will be allowed to split the word. In Microsoft Word, this is done by using Ctrl+-. This hyphen is invisible, unless the word gets split at the end of a line.
But as a rule of thumb, see if the word is still easy to understand if you say it out loud with a pause where you are going to break the word. Usually, try and split it in the middle of the word.
But, as you can see, it just makes it harder to read. Just don't do it.
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