I am seeing both 20$ and $20 usages. (20 is nonessential to this question.)
What is the difference between them?
I am seeing both 20$ and $20 usages. (20 is nonessential to this question.)
What is the difference between them?
It is the convention of some countries to put their currency symbol before the number, while others put it after the number.
At least one country has put it in the middle.
So you could assume, in the absence of any context, that the 20$ is a different currency to $20.
In English, the dollar sign is placed before the amount, so the correct order is $20, as others have noted.
However, when you see people using 20$, it's likely they're being influenced by a few different things:
Because of these inconsistencies, writing 20$ is a very common mistake. I've been known to do it myself.
In American English, the currency symbol is placed before the amount; the same is true for British English.
It is $20, not 20$.
The location of the currency depends on the language in which it appears.
For instance, English texts should use "€ 20" while French ones should use "20 €".
As others have mentioned in passing, those are not the only two possibilities. In France at least, you sometimes find prices written as 19€95, as an alternative to 19,95€ (and yes, the decimal separator there is the comma).
20$ is French-Canadian and $20 is English-Canadian/American.
For dollars, the correct way is $20. When I see 20$ it means the writer was thinking "twenty dollars" (not "dollars twenty") and accordingly it is natural to type 20$ and if the writer is feeling lazy she will not backspace to correct it. Laziness is more common in casual contexts.
$20 is conventional, but to throw a wrench in the whole thing: if it is casual correspondence, either way is OK.
Why all the overcomplication? The difference is that, in English, $20 is the correct way to use the dollar sign, while 20$ is an incorrect way to use the dollar sign. That's all there is to it.
Other languages and currencies are irrelevant to the question. Heck, how the cent sign is used is irrelevant to the question, even though it is arguably the same currency and definitely the same language.
I think that part of putting the symbol preceding the number is to help differentiate between dollars and cents. The dollar symbol always precedes, while the cent symbol always follows. If both were to followed, this could potentially become confusing, as a roughly written S with a vertical strike could be mistaken for a c with a vertical strike.