There are shops at either end / both ends of the street.

either side/end/hand etc

both sides, ends, hands etc[= each]:

He sat in the back of the car with a policeman on either side.

There are shops at either end of the street.


I have seen the definition and then I was wondering if either side and both sides are interchangeable for the same meaning like There are shops at both ends of the street and He sat in the back of the car with a policeman on both sides?


So can we say either and both are sometimes interchangeable for the same meaning, but sometimes they are not, right?


What do you native English speakers think? Thank you so much in advance.