Source: An Introduction to Language (10 ed, 2014) by V Fromkin, R Rodman, N Hyams. I already read this.
[p 578:] root = The morpheme that remains when all affixes are stripped from a complex word, e.g., system from un + system + atic + ally
[p 581:] stem = The base to which one or more affixes are attached to create a more complex form that may be another stem or a word; see root, affix.
[p 597:] base = any root or stem to which an affix is attached.
[p 43:] In the preceding example [at the bottom of p 42], system [...] are bases.
I know that the Ancient Greek etymon of 'system' comprises two morphemes, but which the authors never revealed and so to which the authors are not referring.
How does the definition above imply that the English noun 'system' is a base?
'system' has no affix attached!