Answer:
The difference is the combining vowel
Explanation:
The Combining form needs the vowel to form, that is:
root word + combining vowel = combining form
Root word:
A root is a word that does not have a prefix in front of the word or a suffix at the end of the word. The root word is the main lexical unit of a word and a family of words, which carries the most significant aspects of semantic content and cannot be reduced to smaller components
Combining form:
Training process of words from two or more roots or simple words.
When the word includes a cultured base and a patrimonial base, we will consider derived word. For example, hypermarket, bi-monthly
