I am used to modify a sentence.
I can be used between two letters, and I can be used to swap two letters.
My prefix is commonly used, and my suffix is sometimes found in remote places.
What am I? One word.
There are 5 clues above; there should be 5 explanations.
You are a
Commute
I am used to modify a sentence.
A judge can commute a sentence.
I can be used between two letters, and I can be used to swap two letters.
You can commute from A to B or you can use the Commutative Property in math.
My prefix is commonly used,
Com is short for common.
and my suffix is sometimes found in remote places.
The mute button is found on a remote control.
It might be a long shot, but is it possible that the word is
rule?
I am used to modify a sentence.
In law, a rule is defined as an order made by a judge to modify a sentence
I can be used between two letters, and I can be used to swap two letters.
These are similar in that they could refer to math. You can use a rule between two letters (ie variables):
a > b. In a similar way, you can use a rule to swap two letters:a = b. While I naturally considered math/programming rather than regular English, seeing that you're a mathematician from your profile further influenced my decision to stick to this meaning.
My prefix is commonly used
A bit of a long shot but the most common use for the prefix (RUL) is within the medical field, meaning Right Upper Lobe [of a lung]. Our lungs are pretty commonly used, I'd say.
my suffix is sometimes found in remote places.
Again, unlikely, but a Ule is a type of tree that can be found in rainforests of Mexico, Central America, and northern South America. A rainforest is more often than not considered remote, as it is far from civilization and difficult to get to.
