This may be a stupid question, but which one are the root word in Esperanto nouns or verbs? It looks to me like nouns are the root because of this

word + -o = noun -> remove -o add -i = infinity form of the verb base on the noun -> remove -i add -e = adverb to modify another verb but base on a noun.

That brings me to my second question. the "diagram" above look like a good way to expelling affixes, and maybe correlatives, in Esperanto. So, I was wandering if anybody will like to help me make a more complete "diagram" like the one above but with all the affixes and correlatives? It will be posted here, on a new thread, to help others learning Esperanto.

Actually, the subject is more complex and not so easy to explain. There is a scientific paper on this issue (Radikoj kaj vortoj en esperanto ) but I'm not sure if it is very helpful in learning Esperanto.

To answer your question without requiring you to read complex scientific papers in Esperanto - some roots are considered to be inherently nouns and some are considered to be inherently verbs and some are considered to be inherently adjectives.

For example, you can see why rugx/ (red) would be an adjective root, why dom/ (house) would be a noun root, and why far/ (do, make) would be a verb root. In most cases a root has an obvious "native" category. There are some borderline cases where it isn't obvious (comb -- we comb hair with a comb, so is this a noun or a verb root in Esperanto?). In those cases you just have to memorize it (usually by learning the Esperanto definition of the words).

Some people have said that this system is too complicated. But I think that if the creator of Esperanto had arbitrarily said "all roots are verbs" or "all roots are nouns", we would have ended up with a system that is more complicated in the end. Not every noun has an obvious verb to go with it, and vice versa.

erinja:To answer your question without requiring you to read complex scientific papers in Esperanto - some roots are considered to be inherently nouns and some are considered to be inherently verbs and some are considered to be inherently adjectives.

For example, you can see why rugx/ (red) would be an adjective root, why dom/ (house) would be a noun root, and why far/ (do, make) would be a verb root. In most cases a root has an obvious "native" category. There are some borderline cases where it isn't obvious (comb -- we comb hair with a comb, so is this a noun or a verb root in Esperanto?). In those cases you just have to memorize it (usually by learning the Esperanto definition of the words).

Some people have said that this system is too complicated. But I think that if the creator of Esperanto had arbitrarily said "all roots are verbs" or "all roots are nouns", we would have ended up with a system that is more complicated in the end. Not every noun has an obvious verb to go with it, and vice versa.

Thank you

In most dictionaries the first translation of the root word is by its grammatical cethegory.
E.g.
kis/i to kiss; ~o a kiss
komb/i to comb; ~il/o a comb
or/o gold; ~a golden
ruĝ/a red; ~o redness

erinja: In most cases a root has an obvious "native" category. There are some borderline cases where it isn't obvious

Is there a list anywhere of these "borderline" cases?
It would be far simpler to memorise these exceptions than to be wondering if one has correctly guessed the root class of a word.

Bemused:Is there a list anywhere of these "borderline" cases?
It would be far simpler to memorise these exceptions than to be wondering if one has correctly guessed the root class of a word.

Look to the dictionary. The first meaning, in most cases, defines the class of word. The class of English word may be other than as the class of its Esperanto translation.

Reta Vortaro:
kombi
(tr) Malkonfuzi, purigi, ordigi per kombilo: kombi barbon, harojn; sin kombi; kombi hundon.

kombilo
1. Ilo el korno, celuloido, metalo kc, kun longaj maldikaj dentoj por malkonfuzi, purigi, ordigi la harojn.
2. Analoga ilo, kiun uzas la virinoj por fiksi aŭ ornami sian hararon.

"kombi" is the first, "kombilo" is the next. This means that "komb-" is verb root.

Oxford Dictionary:
comb n 1. piece of metal, plastic etc. with teeth for making hair tidy ...
vt, vn 1. use a comb on the hair ...

"a comb" is the first, "to comb" is the next. Thus, should I think that "comb" is noun root in English?

Bemused:

erinja: In most cases a root has an obvious "native" category. There are some borderline cases where it isn't obvious

Is there a list anywhere of these "borderline" cases?
It would be far simpler to memorise these exceptions than to be wondering if one has correctly guessed the root class of a word.

I am not aware of such a list but I've never gone looking for one either, so someone may have made up a list of words that they personally had trouble with. But it would vary based on native language; an English speaker's obvious verb might be an obvious noun for a speaker of another language.

Brush and comb are well-known examples. Brush is a noun root in Esperanto, comb is a verb root. So you brosi with a broso, but you kombi with a kombilo.

Any Esperanto dictionary will take one part of speech form of a word and list and define that first. Largely the meanings of the other parts of speech relate in a more or less systematic way to the meaning of the head word.

It is easy to find examples of this. Thus if KOMBI (to comb) is the head word, then KOMBILO is the toothed implement, but in the case of the head word BROSO (already meaning a brush) we do not say brosilo , and the verb to brush is BROSI.

There's a grammatical theory that the roots (ie the word without the part of speech ending) are themselves of a certain part of speech type. But this theory is not without problems.

As a beginner, you do not have to concern yourself too much with this theory. For derivations just go by the meaning of the first word in the dictionary entry.

There is no point in learning a list of 'exceptions', just learn the words. In fact many fluent Esperantists might, in particular cases, be hard pressed to say whether a root belongs to this or that class. However they will know how to use the the adjective, verb, noun etc that share the root.

What makes Esperanto easy is that, for example, having learnt that luno means moon, you don't have to think very hard to find a word for lunar (it's luna). Also you won't make the mistake of supposing that luni means to moon (in its English meaning) since that is not directly related to the meaning of luno.

And even if it doesn't strictly follow the root class analysis it comes as no big surprise that manĝo is a meal, given that manĝi means to eat (or vice versa for that matter).