Sociolinguists must use the term differently from ESL teachers.
I think I made this point in the last thread - not sure.
To a linguist, a second language is a language that is widely spoken in the community, but not one's native language, such as a native Hindi speaker learning English in India, or a Hokkien speaker learning English in Singapore.
English is not "foreign" in these countries.
A foreign language to this same person would be something not spoken as a widely functional language in their country, such as Spanish or Irish.
In largely monolingual countries like Australia, almost everything except English is a foreign language.