Questions & Answers about Alter anser e stagno exit et ad litus venit.
Alter most often means the other (of two). So if two geese are already understood in the context, alter anser means the other goose.
In some beginner-level contexts, it can feel like another or a second. But its most precise core idea is one of two, as opposed to the first.
This is a very common question.
- alter = the other of two
- alius = another / a different one more generally
So if exactly two geese are in the picture, alter anser is the natural choice for the other goose. If you just meant some other goose without a two-way contrast, alius would be more general.