When do you use which? Or are they interchangeable?

second=deuxiéme
so in what pretext are you planning to use it?

... or rather in what context were you thinking, Fifi?

Merci. I was just curious because I've heard mostly "deuxieme" except in ballet class where 2nd position is "a la seconde."

now yes a la seconde lieu expresses place or placing like in a ballet dance. Deuxieme is the more usual english second like second floor,deuxieme etage

Use "deuxième" when there'll be a third (troisième). Use "second(e)" when there's only two choices (premier(e) et second(e)).
i.e.: deuxième étage & seconde classe. Having said that, noone really says "seconde classe". Maybe because there was once a third class...

quote:

Maybe because there was once a third class

actually it is because there were a first class on the local banlieux trains and it is no more.
the trains are still marked but is not spoken of anymore.
everybody is "first class" French egalité. Now if you go to the TGV then all hell breaks loose.Vive la diference.