Language/English/Vocabulary/At-first-and-first

At first and first

We use "at first" to talk about the beginning of a situation, to make a contrast with something different that happens/happened later. "At first". . . is often followed by but. 

Examples:

At first they were very happy, but then things started going wrong.

The work was hard at first, but I got used to it.

In other cases, we usually prefer first. 

Examples:

That's mine - I saw it first! (not . . .I saw it at first.)

We lived there when we were first married. (= . . . in the early days of our marriage.) (not . . . when we were at first married.)

First, I want to talk about the history of the problem; then I'll outline the situation today; and then we'll discuss possible solutions, (not... At first, I want to talk . . .)