Ago

Ago is a word used to describe the time length since something happened. It is always used with a period of time. You can say that something happened 20 years ago, 20 days ago, or even 20 minutes ago. It shows really well when something happened in the past.

Take a look at the following examples to understand its usage.

• John moved to France 20 years ago.

• I suffered from headache 20 days ago.

• He was here 20 minutes ago.

• His mother retired 5 years ago.

It becomes clear that ago is a word that is used to indicate something that happened at a particular point of time in the past. Ago indicates a past event.

Before

Before is also a word used to indicate something that took place in the past but there is no particular times frame that before talks about. For example, if you have visited a place before, you are not required to specify the date or time when you were there.

Before refers to a moment. it can be either in the past or in the future, so something happened or will happen before a moment

Examples: He came (will come) before the meeting.

What is the meaning then when we use before with a period of time, and can we say "He came before 20 minutes" I can say this, but I am referring to the particular moment 20 min ago.

He came before the meeting

The meeting started 20 minutes ago, so he came before 20 minutes ... or he came before that moment 20 minutes ago.... And it is not clear particularly when.