Emphasizes an extreme or unexpected example; often follows a noun or noun phrase. Similar to さえ but slightly more emphatic.
See also: さえ
子供でさえその問題が解ける。
Even a child can solve that problem.
彼は簡単な漢字でさえ読めない。
He can't even read simple kanji.
Used in conditional clauses after a noun or na-adjective; implies that the stated condition is sufficient. Often appears with ば, たら, or なら.
See also: さえ
If only I had free time, I'd like to go on a trip.
元気でさえいれば、何でもできる。
As long as you're healthy, you can do anything.
でも can also mean 'even' in certain fixed phrases, but it usually means 'but' or 'even if', unlike でさえ which always emphasizes an extreme example.
Compound of particle で and さえ (even). The exact historical development is uncertain, but it functions as an emphatic form of さえ.