This is the 11910th most frequent Spanish word.
idéntica
Identical.
Here, 'idéntica' is used as an adjective to describe the similarity between the replica and the original painting.
La réplica del cuadro es prácticamente idéntica al original.
The painting replica is practically identical to the original.
In this case, 'idéntica' is describing the identical nature of the appearance of the twin sisters.
Las hermanas gemelas tienen una apariencia idéntica.
The twin sisters have an identical appearance.
'Idénticas' is employed to emphasize that the copies are the same as the original document.