Is there a word for this part of a word?!

[sunnywinters]

In a word with a suffix, is there a word for the part of the word that's not the suffix?!

For example, with the word "wonderful", is there a term for the part that's "wonder"?

The stem or base word.

It is called the root word.

Root word

Afaik root means the very central part of the word which brings the basic meaning, but it doesn't generally describe everything before the suffix.
Take a word "ungrateful" - the root is "grate", but simple removal of the suffix leaves "ungrate". I am not aware of any word for this.

As for the stem, afaik proper stem removes the prefixes as well (thought I met "stemming algorithms" which removed only the end of the word).

Btw:
"Ungratefully" - would you say it has two suffixes?
"Commanders" - would you say it has one suffix "er" and one ending "s", or two suffixes as well?

Anything added to the front of the word is a prefix, anything added to the end is a suffix. The original is the root word.
Root word - happy
Add prefix un - unhappy
Add suffix ness - happiness
Add both prefix & suffix - unhappiness

The stem