At first / First

[Adella]

Hello!

Are these fully interchangeable at the beginning of a sentence when we enumerate things in the present tense, e.g.

First/ At first a theoretical concept of xxx is dealt with. Secondly, a number of xxx are discussed.

[Alan]

Hi Adelia,

'First' and 'firstly' usually introduce a list of things/activities/procedures. 'At first' usually suggests 'to start with' 'at the beginning' and doesn't necessarily introduce this type of list.

First(ly) we had to book our hotel room then we checked the availability and finally we had to pay in advance. At first I thought it was rather expensive but I realised that it was an average price.

Alan
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English as a Second Language
You can read my ESL story Present Simple