Hyphen Vs Dash

The Hyphen

The hyphen is used between two words to directly join them together to create either a compound adjective or a compound noun –– 'compound' meaning a whole formed of multiple components. It is otherwise referred to as the n-dash, for, traditionally, it has the length of the lowercase letter 'n'.

Examples of usage for compound nouns: Jean-Paul, sheep-dog, bear-hunter, soul-stealer… Examples of usage for compound adjectives: oft-cited, light-red, well-known, green-blue…

You will notice that the compound nouns are formed of individual nouns which, alone, have their own meanings and definitions –– 'soul' and 'stealer', for example –– but, when combined, so too are these meanings, and the nouns together read differently –– 'soul-stealer' now means specifically a stealer of souls.

You will also note that some of the compound adjectives are often formed first of an adverb and second by an adjective. These combine together with the hyphen to create one meaning. When such compound adjectives are used after the noun they describe, instead of before it, the hyphen is lost…

Examples: the often-repeated quote has been… vs the quote is often repeated and has been… the well-known city… vs the city is well known…

Similarly, adverbs ending in 'ly' do not require a hyphen when placed before the word they modify:

The chillingly interesting novel… A beautifully handcrafted table… Some wonderfully smelling flowers.

The Dash

Otherwise referred to as the m-dash, for, traditionally, it has the length of the lowercase letter 'm', the dash is used to provide the reader with supplementary, and usually shocking or surprising, information.

I found the shoes –– which were a dazzling red! –– by the fireplace. The aeroplanes –– or were they UFOs? –– often flew over our house. I saw the children –– the children of Thomas and Simon –– playing in the field.

You will notice that the clause within the two dashes can also be punctuated.

You can think of the dash as a form of parenthesis (brackets), but they are used specifically for tonal or stylistic variation, to add suspense, intrigue or additional and perhaps unnecessary information, whereas brackets, for instance, are used mostly to introduce additional information for clarification purposes.