1Indicates that something has already happened; similar to 'already', used to show completion or that a fact is established.
会議はすでに始まっている。
The meeting has already started.
その本はすでに読んだ。
I've already read that book.
すでに支払いは済ませてあります。
The payment has already been made.
2Indicates that something occurred prior to a certain point; means 'previously' or 'before'.
彼はすでにその会社を辞めていた。
He had already left that company.
その噂はすでに村中に広まっていた。
That rumor had already spread throughout the village.
このデータはすでに収集済みだ。
This data was collected beforehand.
3Used for emphasis or strong assertion, similar to 'indeed' or 'as already mentioned'; a somewhat literary or emphatic usage.
すでに述べたように、対策は必要だ。
As already mentioned, countermeasures are necessary.
彼の実力はすでに周知の事実だ。
His ability is already a well-known fact.