Ago = before â€˜nowâ€™, the moment of speaking (earlier than the present times); in the past: â€˜Her plane landed ten minutes ago. In fact, here she comes now.â€™ â€˜I saw him just five minutes agoâ€™ (five minutes before now). â€˜Two years ago I came to the US.â€™
Before = before â€˜thenâ€™, a time in the past; previously: â€˜I went to the airport last Monday to meet Sue. I hadnâ€™t been to the airport before.â€™ (= before last Monday). â€˜I saw him last Friday in London and two days before in Leeds.â€™ â€˜As I said before, the work should be completed within Mondayâ€™ (Previously).
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