What the 16 rules leave out, and why they never changed

What the sixteen rules do not say

The rules hold every ending in the language. They do not hold the language. None of these is in them:

A note on four of them:

• Affixes. PMEG counts ten official prefixes: bo- ĉef- dis- ek- eks- ge- mal- mis- pra- re-. Many textbooks add fi- (fihomo, a scoundrel), which the Fundamento has only as an exclamation. See word building.
• Correlatives. All forty-five come from one grid: correlatives.
• Word order. La katon vidis la hundo. - The dog saw the cat: the -n, not the position, marks the object. See word order.
• Capitals. The Fundamento writes Januaro with a capital, and PMEG still recommends it; many now write januaro. See capital letters.

The rules never grew

The Akademio de Esperanto adds words and gives advice. It cannot touch the sixteen rules, and in more than a century nothing has:

• La domo estis konstruita. - The house was built (finished: the 1967 reading).
• Francio and Francujo - France: both in use, and the Akademio accepted -io in 1974. See countries and peoples.

For a learner the consequence is simple: the grammar you have learned is the grammar, and there is no second edition.