adverb
1
BAD : Before forty years the journey took twice as long.
GOOD : Forty years ago the journey took twice as long.
BAD : Not so long before we used animals for transportation.
GOOD : Not so long ago we used animals for transportation.
◆◆◆
ago = before 'now', the moment of speaking: 'Her plane landed ten minutes ago. In fact, here she comes now.' 'I saw him just five minutes ago.' (= five minutes before now)
before = before 'then', a time in the past: 'I went to the airport last Monday to meet Sue. I hadn't been to the airport before.' (= before last Monday). 'I saw him last Friday in London and two days before in Leeds.' (= last Wednesday)
2
BAD : My parents first came here before 40 years ago.
GOOD : My parents first came here 40 years ago.
3
See EVER 2 (↑ ever )