Why do you use hyphen in some words?

Answer 1

Some multiple-word terms are easily read as one word, while other sets of words need to be hyphenated either for ease of visual interpretation and pronunciation, or simply to keep the end result from becoming unwieldy.

Many words we routinely use as a single word today were once hyphenated; others that today are hyphenated will probably remain so. For example, the term milk shake can be equally correctly written 'milk shake', 'milk-shake' or 'milkshake': none of the three appears especially wrong, though the two-word version is less common today. One day the term will probably lose its space, and later its hyphen, forever. The term two-word, though, would look clumsy written as twoword, and would be difficult to pronounce, especially for those learning English. But if we write, '… the two word version …' it could lead to misinterpretation. The term 'two-word', in this case, needs hyphenating, unless we want to write, '… the "two word" version …', which some might consider clumsy.

On the other hand, the word 'coordination' is today routinely written without a hyphen, but some people still prefer 'co-ordination', feeling uncomfortable pronouncing (and we all mentally pronounce words as we read them) the unhyphenated 'coor-' part of the word.

It's difficult to pin down hard-and-fast (or hard and fast, but not hardandfast) rules in these situations, and there seems little point in attempting to do so, since the only useful aim might be to settle an argument over which expression is ultimately and solely gramatically correct in English. This is fine for purely academic intentions or perhaps to achieve a definitive ruling in a word game (or word-game, but possibly not yet a wordgame), but for all practical purposes such questions simply come down to common usage.

If the majority of people use words or phrases in a certain way, this is how most speakers of the language will feel comfortable in expressing those terms; this is, in other words, common usage - the ultimate decider of right, wrong, maybe, or maybe not, in any discussion on language. It is the users of any language who ultimately decide how that language is used.

So in the end you'll very likely be safe to consider how you feel about the way any idea is expressed: if it sounds good, looks fine, and you feel okay with it, you're probably right.