indistinguishable
adj.so similar to something else that you cannot see any difference between them.
adj.impossible to differentiate or tell apart from something else. Often used with the preposition 'from'.
“The fake watch is indistinguishable from the real one.”
“To the untrained eye, the two species of butterfly are indistinguishable when they are in flight.”
“Advances in synthetic materials have made some artificial fabrics indistinguishable from natural silk in both texture and appearance, even to experienced textile experts.”
Typically used predicatively after a linking verb and followed by the preposition 'from'.
The adjective 'indistinguishable' typically takes the preposition 'from' to indicate the point of comparison.
“Visually, the Touring is mostly indistinguishable from the more expensive Grand Touring, which is fortunate because its design is one of the vehicle’s strongest assets.”
“Inevitably, these carefully curated images presented the four grand duchesses as largely indistinguishable sisters who went everywhere in matching white dresses , their expressions serene but somewhat inscrutable.”
From in- + distinguishable.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.