first / last

[hela]

Dear teachers,

Are “first / last” adjectives, adverbs ?

1) I came in first this semester.
2) I came first on the first day of class.
3) The first thing I do when I come home is…

How should I know which parts of speech first/last belong to?

Thank you for your help.
Hela

[Casiopea]

Look at where the word sits in the structure. For example,

2) I came first on the first day of class. (determiner + adjective + noun)