"Inter-", "multi-", "cross-", "trans-" in relation to disciplines

Combining form:

noun

Grammar
A form of a word normally used in compounds in combination with another element to form a word

ODO, emphasis mine

Combining forms tend to be words or roots that are combined with other words to form compound words.

Prefix:

1 An element placed at the beginning of a word to adjust or qualify its meaning (e.g. ex-, non-, re-) or (in some languages) as an inflection.

ODO, emphasis mine

Prefixes tend to be word elements that were Latin prepositions, which could also be used as Latin prefixes to add limited relational meaning to other Latin words. Words with these prefixes are not generally considered compound words.