Why is 'hyper-' considered a prefix, but 'tachy-' is considered a combining form?

Question

I am learning medical terminology. My medical terminology textbook has me all confused about roots, prefixes, suffixes, and combining forms; so I have been doing some research. I've found that most dictionaries I've referenced have a different concept of a combining form versus a prefix or suffix. But even using the concept proposed by the dictionaries, I'm having trouble. Follow this link to see how Merriam-Webster distinguishes combining forms and affixes: https://www.merriam-webster.com/dictionary/combining%20form. For example, the online Merriam-Webster dictionary refers to 'hyper-' as a prefix, but "tachy-" as a combining form. I don't understand how Merriam-Webster came to that conclusion. Any insight you can provide would be greatly appreciated. Thanks.

Answer 1

So as I understand it based on the Merriam Webster, a combining form needs a suffix or a prefix to obtain lexical meaning. A prefix or a suffix cannot obtain lexical meaning by way of another prefix or suffix. So, in the example they give: cephal- in cephalic (a suffix ic is added to cephal). However, should I have hypo, I need to attach it to a combining form rather than a prefix or suffix. I probabably can't say hypic for instance.