What is the difference between 'curricula' and 'curriculum'?

What is the difference between 'curricula' and 'curriculum'? Both appear to have the same definition. Are they used in the same context?

Solution 1:

Curricula is the plural of curriculum.

Solution 2:

Curriculum is a collection of subjects taught and is a singular noun. Its plural form is curricula or curriculums.

For example, we can say

The two schools have different curricula.

Similarly, the plural of referendum is referenda or referendums.

Solution 3:

Curricula is the plural of curriculum.

This question, asked in a more general way, might be, "What is a common way of forming plural vs. singular for Latin-derived words?" There is a whole list of them and they come in multiple patterns:

• curriculum vs. curricula
• referendum vs. referenda
• datum vs. data
• medium vs. media
• focus vs. foci

There are certainly more, but these come to mind.