Identical
Definition 1 of 3
Pro Tip 1/3
Look Alike
Used when two objects or people look exactly the same and are hard to distinguish. The paintings were identical, making it difficult to identify the original.
Pro Tip 2/3
Mirror Image
Often refers to the sameness that you'd see if one was the reflection of the other. The puppies were identical, like mirror images of each other.
Pro Tip 3/3
Not Interchangeable
Two items may be identical but still serve different purposes or belong in different places. The keys were identical, but only one would open the safe.