So, it's a request post and I decided to publish it here.

Explain Dash and Hyphen

Before, started this topic, do you know the difference between them?

Here, start with this-

A hyphen is a short black line with no spaces around it-like that.

A dash is a slightly longer black line, with spaces around it – like that.

Got it?

Now let's understand them individually.

Hyphen

Let’s start with the hyphen which, though smaller than the dash, has a heavier responsibility. The hyphen has three main uses:

-To join a prefix to a word
-To make a compound word
-To indicate a word break

1. Hyphens join prefixs

A hyphen is the glue that joins a prefix to a word. Here are some examples:

post-apocalyptic  
pre-natal  
co-author  
re-consider (whether to use a hyphen)

Yes, you may have to reconsider, because the use of a hyphen to join prefixes is becoming less common. More and more words are joined at the hip, not by a hyphen, to make a stand-alone word. (Or a stand alone word. Or even a standalone word.) You can probably think of loads of words that begin with ‘post’, ‘pre’, ’co’ and ‘re’ that don’t have a hyphen.

Example - 

So, did we re-cover a couch, or recover a couch?

Clearly there’s an ambiguity. If we re-cover the couch, we’re giving it some groovy new upholstery and a new lease on life.
If we recover it, we’re rescuing it from the hard rubbish pile outside the neighbour’s house.

See the difference? A hyphen helps prevent ambiguity.

2. Hyphens from compound words

Well, this is bit lengthy and technical topic so if you want to understand it better, I suggest you to get a good dictionary or something.

But let's give you a short explanation which I got from a very useful website:

Compound adjectives (descriptive words)

Rule of thumb – use a hyphen.

up-to-date rules of grammar  
award-winning novelist  
six-year-old boy

That seems pretty straightforward, but there are a couple of important exceptions to this rule. The first is no hyphens in compound adjectives when the first word ends in ‘ly’.

friendly looking grizzly bear   ✔
friendly-looking grizzly bear  ❌

quickly written blog post   ✔  
quickly-written blog post❌

Compound verbs (action words)

Rule of thumb – use a hyphen.

touch-type  
sight-read  
blow-dry

There are, however, exceptions. Proofread is one word – for no apparent reason. So do consult a dictionary if you’re not sure.

More exceptions are phrasal verbs, which is a show-off way of saying a verb made up of a main verb and adverb or preposition (small word, usually).

She built up (not built-up) a huge amount of frustration over whether to hyphenate.

Note, however, that we should write:

a built-up area ✔
a built up area.❌

That’s because in this case ‘built’ and ‘up’ form an adjective.

Hyphens with numbers – a special case

This is where the hyphen really comes into its own.

Use a hyphen in a span of dates or numbers:

the 1939-45 war  
pages 23-32  
sections 10-13  

An exception is when using the word ‘from’:

the war lasted from 1939 to 1945 ✔   the war lasted from 1939-45❌

read from page twenty-three to page thirty-two

And, as you can see from the example above, you should always use a hyphen when writing compound numbers as words.

Twenty-one  
eighty-six  
ninety-nine

3. Hyphen indicate word break

This is a rare event in the computer age, but if you’re hand-writing a letter and run out of room to finish ‘Rumpelstiltskin’, you need to pop in a hyphen before finishing the word on the next line. It’s a good idea to put the hyphen in a sensible place. So:

Rumpel-

stiltskin ✔

is better than

Rumpe-

lstiltskin ❌

******

Phewww, that was not easy :/ I hope you are getting it.

Let's review a quick example :-

They had a long-term relationship.

The fire-proof vest proved to be a great life saver for Santa Claus.

If the adjectives come after the noun, then they don’t need a hyphen. For example-

Their relationship was long term. 

Santa’s new vest is fire proof.

Now got something? It was better to understand, right?

Sometimes, the placement of a hyphen changes the meaning of your sentence.

Let’s say you want a “hot-water bottle.” With a hyphen between “hot” and “water” you clearly want a water bottle for holding hot water because “hot” and “water” are joined by a hyphen.

Without the hyphen between “hot” and “water," you might want a water bottle that is hot.

See how the presence or absence of a hyphen could change the meaning?

Now, some people will say that they don't need to use Hyphen.

You probably don’t need the hyphen, but it’s not wrong to use it either because someone probably could be confused.

The more likelihood there is for confusion, the more you need a hyphen.

***********************************

Dashes

Dashes are easier to understand than hyphens. Essentially, they’re used for dramatic effect. In other words, they make a more emphatic, abrupt break in a sentence than other punctuation marks.

They can be used instead of a pair of commas for emphasis:

She was confused by hyphens – those pesky little word-joiners – until she read today’s blog post.

Or to make a complex sentence that needs lots of commas more readable:

He found making a selection from the myriad punctuation marks available in the English language – commas, semi-colons, dashes, parentheses, colons and ellipses – a cause of acute choice anxiety.

Dashes can replace brackets:

Of the punctuation marks in the English language – all fourteen of them – the dash is the most dramatic.

Dashes can also make jokes: :D

She stepped gracefully from the limousine – onto a waiting banana skin.

See how the pause creates comedy?

So don’t stress over hyphens and dashes. If you remember the rules of thumb for compound words and get yourself a good dictionary, you’re half way there (or do I mean half-way?).

Wherever you put your hyphens, placing them consistently is the key to feeling confident.

Source - Different web sources.

(I hope it will help you! - IEscapist )