Esperanto roots usually have the base word, in this case atleto, and other words are derived from that. The base word is often picked based on similarities to other languages, and in this case the similarity is atleto=athlete=(insert many other European languages here).
The same with homo – it's homo, not homulo, homisto, homanto etc.
You can often notice that similar pairs of words have different root choices. The most obvious examples are countries: for most European and Asian countries Esperanto uses the base word for the inhabitants, and for most American countries for the country:
Germanio – Germano
Kanado – Kanadano
So, this is very interesting. I had a conversation with "Amuzulo" (Chuck Smith) and it was his position (or perhaps the position of the early contributors to the course) that the word prezidento (president, as in head of state) would not be taught in the course because prezidanto has a broader meaning which includes the head of state meaning. Therefore, the thinking went, you can always say prezidanto and you don't need to learn prezidento.
It seems, my dear learners, that you have been sold a bill of goods. You actually do need to learn the difference between:
- prezidento - president (head of state)
- prezidanto - president; one who presides - often of a club or company.
Your sentence means "This president is not presiding."
What you wanted to say is this:
- Tiu prezidento ne estas prezidenta - This president is not presidential.
Damn. That was subtle.
Even so I should've known this, because the affix -ant- was somewhere in the previous lessons.
BTW, Vortao doesn't recognize lots of the words I look up (eg presidanta, presidenta). That doesn't mean you can't make these words, does it? I mean when there's no conflict with another rule or something (like where the verb derived from an adjective turns out a transitive one).