The expressions firstly, first of all, secondly, thirdly, lastly, finally, to begin with, to start with, for one thing, for another thing etc are used to show the structure of what we are saying.
Firstly, secondly, thirdly, lastly etc
The words firstly, secondly, thirdly etc can introduce the items in a list. Note that we use lastly to introduce the last item in the series.
- Firstly, we need to eradicate poverty. Secondly, we need to create more jobs. Thirdly, we need to increase productivity. And lastly, we need to cut down expenses.
Finally can introduce the last element in a series.
- We must create more jobs. We must increase productivity. And finally, we must compete in overseas markets.
Note that firstly, secondly and thirdly are more formal than first, second etc. These are more common in British English.
The expressions to start with, for another thing etc are also used to introduce the items in a list.
- There are three reasons why I don’t want to marry him. To start with, he doesn’t have a good job. For another thing, he is younger than me. And thirdly, my mother doesn’t like him.