Two things are identical when there is no difference between them at all. Two prints from one negative; brothers you cannot tell apart; the flat you are standing in and the one above it, down to the crack in the tiles.
Identical takes to in everyday British English - identical to the original - and with in formal or technical writing: identical with the sample. Identical as and identical than do not exist. The word has no degrees, because there is nothing beyond exactly the same, so almost identical works and very identical does not. Identical twins grow from a single egg and share their genes; non-identical twins do not, whatever they look like. The noun is identity, the adverb identically, and the near word to keep separate is similar, which leaves room for difference where identical leaves none.
1adjectiveidenticalExactly the same in every detail.~64%
“The two signatures are identical, right down to the loop on the second letter.”
synonyms: indistinguishable, matching
2adjectiveadjectiveThe very same one.~2%
“We were reading the identical page and still disagreed about it.”
3adjectivegrownGrown from a single egg, and so alike, said of twins.~34%
“The identical twins in the front row swapped seats to confuse the supply teacher.”
Shares are an estimate: a language model read 20 sentences found in the wild and placed 20 of them on a sense — a count of our sample, not a measurement of English.
From identic + -al.
Etymology from Wiktionary, CC BY-SA