What is the opposite of "abbreviation"?

What is the opposite of "abbreviation"?

For example, if ELL is an abbreviation for English Language Learners,
then English Language Learners is a(n) _{_______} for ELL.

I'm looking for a word that will work for all abbreviations, not just acronyms, so another example would be: if abbr. is an abbreviation for abbreviation, then abbreviation is a(n) _{_______} for abbr.

Solution 1:

I'd go with expansion if I were forced to fill in the blank (although I'm more comfortable with expansion of than expansion for). You can expand an acronym.

However, it would be more usual to say:

What does ELL stand for?

Or:

ELL stands for English Language Learners.

Especially in non-technical contexts, stand for sounds more natural to my ear.

Solution 2:

It is called the full form of an abbreviation.

Solution 3:

I've always gone with the somewhat lengthy but accurate "long form."