"He speaks while sleeping."
Translation:그는 자면서 말합니다.
면 would mean "if" and its attached to the sequential form of a verb/adjective (하다 -> 하니 -> 하면. 먹다 -> 먹으니 -> 먹으면. If the verb/adjective has a ㄹ stem, the ㄹ does NOT drop out, so 날다 would go to 날면, despite the sequention form being 나니). 면 Can also be added after the plain informative form of a verb/adjective. E.g. 하다 -> 한다면. 먹다 -> 먹는다면.)