A: 同じです (I said)
B: 同じくです (A native Japanese speaker said)
The 終止形 of 同じく is 同じい, but it seems they have the same meaning
Is there any difference between them, anything makes A and B sound different?
Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It only takes a minute to sign up.Sign up to join this community
In that context, 同じです and 同じくです work the same, though the former is more common. But that does not mean they are always interchangeable.
同じ and 同じく are not regular adjectives. There is no such an i-adjective as 同じい*, and 同じく is a fixed adverb meaning "likewise" or "similarly". 同じく is typically used when repeating the same opinion or in place of the same word.
*Actually a large monolingual dictionary has an entry for 同じい as an i-adjective, but don't use it in modern standard Japanese. 同じく is the only allowed form.
同じくです is not very common, but it's "Same here" or "Ditto". Thus you cannot use 同じく in the following example: