すでに

すでに means "already": by the time in question, the event has happened or the state is in place. It goes in front of the predicate, usually a た-form or a 〜ている form, and belongs to writing and formal speech.

In business speech and in reports it turns up in set phrases such as すでにごぞんじご存じ ("as you already know") and すでにのべた述べたように ("as stated above").

すでに or もう

In the "already" sense the two mean the same. もう is what you say in conversation; すでに sounds written or formal, the word of news reports, notices and business email.

もう also means "any more" with a negative and "another" before a number. すでに has neither meaning.

• × すでに一つください → もう一つください