Let's recap how the vocabulary in Esperanto is formed.

There are prefixes which come in front of the root and there are postfixes, a.k.a. suffixes, which come after it. There is a limited list of the official pre- and postfixes, and most introductionary books list all of them. In addition there are some inofficial pre- and postfixes which are mainly used in certain special fields, like medicine, engineering, mathematics and so on. Already these pre- and postfixes have a certain character, nature, i.e. what kind of words they are meaningfully combined with. For instance you wouldn't combine the prefix bo- : meaning -in-law (for relatives) with a verb.

The biggest group consists of the roots. The first non-single letter, non-name entry in Plena Ilustrita Vortaro (PIV) is abak/o and the last zum/i. Between those are over 25000 entries (that's a number I found for an older edition). Not counting single letter, name and primitive particle (words like "as", "but" which do not flex in any way) entries, the entries in a good dictionary (like PIV) are marked for vortkaraktero : word character. For instance abak/o is fundamentally a noun, zum/i a verb and bel/a an adjective.

While in theory you can combine any prefix, even a couple ones with any root and any postfix or multiple postfixes, the sheer number of all theoritically possible combinations gets rapidly overwhelming. In practice you take max one prefix and max two postfixes, words with more are usually too hard to decipher, i.e. to understand what they mean.

The characters of the pre- and postfixes and the roots limit even more what combinations are meaningfull even in theory. There is a principle of sufficiency and necessity in Esperanto, it says that you should limit piling up pre- and postfixes to the mimimum to express the idea without it being mixed with another one. For instance martelo means hammer and when you use it you can obviously say like haki kun martelo : to hit with a hammer, but to have a verb it is enough to say marteli : to hammer. There is no need to add more, since the "obvious" action with it is hammering. Of course that "obviousness" is open to interpretations.

Let's recap how the vocabulary in Esperanto is formed.

There are prefixes which come in front of the root and there are postfixes, a.k.a. suffixes, which come after it. There is a limited list of the official pre- and postfixes, and most introductionary books list all of them. In addition there are some inofficial pre- and postfixes which are mainly used in certain special fields, like medicine, engineering, mathematics and so on. Already these pre- and postfixes have a certain character, nature, i.e. what kind of words they are meaningfully combined with. For instance you wouldn't combine the prefix bo- : meaning -in-law (for relatives) with a verb.

The biggest group consists of the roots. The first non-single letter, non-name entry in Plena Ilustrita Vortaro (PIV) is abak/o and the last zum/i. Between those are over 25000 entries (that's a number I found for an older edition). Not counting single letter, name and primitive particle (words like "as", "but" which do not flex in any way) entries, the entries in a good dictionary (like PIV) are marked for vortkaraktero : word character. For instance abak/o is fundamentally a noun, zum/i a verb and bel/a an adjective.

While in theory you can combine any prefix, even a couple ones with any root and any postfix or multiple postfixes, the sheer number of all theoritically possible combinations gets rapidly overwhelming. In practice you take max one prefix and max two postfixes, words with more are usually too hard to decipher, i.e. to understand what they mean.

The characters of the pre- and postfixes and the roots limit even more what combinations are meaningfull even in theory. There is a principle of sufficiency and necessity in Esperanto, it says that you should limit piling up pre- and postfixes to the mimimum to express the idea without it being mixed with another one. For instance martelo means hammer and when you use it you can obviously say like haki per martelo : to hit with a hammer, but to have a verb it is enough to say marteli : to hammer. There is no need to add more, since the "obvious" action with it is hammering. Of course that "obviousness" is open to interpretations.