Rule 11 of the 16 (about word formation) is quoted in my copy of the Fundmenta Krestomatio :

....; la gramatikaj finiĝoj estas rigardataj ankaŭ kiel memstaraj vortoj.

I presume the 16 rules appeared in the La Unua Libro.

That's curious, that "root" appears in the English translation of the Unua Libro, but not in the Esperanto translation in the FK! I wonder whether the translations in other languages had the equivalent of "root" in the 2nd and 3rd of the dek ses reguloj. Can the German-speaking and French-speaking forumanoj reading this comment on the matter?

Miland:That's curious, that "root" appears in the English translation of the Unua Libro, but not in the Esperanto translation in the FK! I wonder whether the translations in other languages had the equivalent of "root" in the 2nd and 3rd of the dek ses reguloj. Can the German-speaking and French-speaking forumanoj reading this comment on the matter?

Sure I can. I'm translating these two rules literally from the German-language version in the Fundamento:

"2. The substantive always receives the ending o. The plural always receives the ending j. There are only two cases: nominative and accusative; the latter is formed from the nominative by adding the ending n(*). The remaining cases are expressed by means of the (sic) prepositions: the genitive by de (von), the dative by al (zu), the ablative by kun (mit), or other prepositions corresponding to the sense. E.g. la patr'o, der Vater; al la patro, dem Vater; la patr'o'n, den Vater; la patr'o'j'n, die Väter (accusative).
3. The adjective always ends in a. Declinations like with the substantive. The comparative is expressed by means of the word pli (mehr), the superlative by plej (am meisten). The word "als" means ol. E.g. pli blank'a ol neĝ'o, weißer als Schnee."

(*) A literal translation of indem die Endung n hinzugefügt wird doesn't seem to be possible in English, but it's possible in Esperanto: per ke la finaĵo "n" estas aldonata.

So the German-language version doesn't use either "root" or "word" (except that the words Zamenhof used for "adjective" and "substantive" are compounds with "word").

Miland:That's curious, that "root" appears in the English translation of the Unua Libro, but not in the Esperanto translation in the FK! I wonder whether the translations in other languages had the equivalent of "root" in the 2nd and 3rd of the dek ses reguloj. Can the German-speaking and French-speaking forumanoj reading this comment on the matter?

Polish version of Fundamento says nothing about "roots" in rules, but in the vocabulary part:

"Everything written in the international language Esperanto can be translated by means of this vocabulary. If several words are required to express one idea, they must be written in one but, separated by commas; e. g. « frat'in'o » though one idea, is yet composed of three words, which must be looked for separately in the vocabulary."