difference in meaning?

Is there a difference in meaning in these two expresions:
can't tell a difference between sth and sth
not to distinguish between sth and sth

I want to write that someone doesn't know the difference in use of 2 things.Which one should I use?

[albertino]

Originally Posted by Unregistered

Is there a difference in meaning in these two expresions:
can't tell a(the) difference between sth and sth
not to distinguish between sth and sth

I want to write that someone doesn't know the difference in use of 2 things.Which one should I use?

(Not a teacher)
Hi, welcome to the forum.
In my opinion, both are acceptable. Apart from these, there are some others expressing the same idea:
"can't tell something apart, distinguish A from B, differentiate between A and B, draw/make a distinction between A and B, and discriminate A from B." Hope that helps.

[chellamuthu]

Originally Posted by albertino

(Not a teacher)
Hi, welcome to the forum.
In my opinion, both are acceptable. Apart from these, there are some others expressing the same idea:
"can't tell something apart, distinguish A from B, differentiate between A and B, draw/make a distinction between A and B, and discriminate A from B." Hope that helps.

Thank you Albertino. You have given a fine explanation.