Fendeto estas tro granda por ke mi aĉetu la tekruĉon.

Fendeto comes from:

• fend- = the idea of a crack, split, or fissure
• -et- = a diminutive suffix, meaning small
• -o = noun ending

So fendeto means a small crack or a little split.

Esperanto has no indefinite article. It has only the definite article la = the.

So:

• fendeto = a small crack / small crack
• la fendeto = the small crack

In this sentence, fendeto without la is grammatically fine. But if you mean one specific crack that both speaker and listener know about, la fendeto might sound more natural.

Tro means too in the sense of more than is acceptable or suitable.

So:

• granda = big
• tro granda = too big

This is the same idea as English too big, not just very big.

Because granda is a predicate adjective after estas.

In Esperanto, adjectives take -n when they modify a direct object, but here granda is simply describing the subject fendeto through the verb estas.

So:

• Fendeto estas granda = The crack is big.

No accusative -n is needed on granda here.

Por ke introduces a subordinate clause meaning something like:

• so that
• in order that
• in this kind of sentence, often for ... to

Here it corresponds to the English structure too big for me to buy the teapot.

Esperanto cannot use the exact same English pattern, so it uses a full clause:

• por ke mi aĉetu = for me to buy / so that I would buy

After por ke, Esperanto normally uses the -u verb form.

So:

• aĉetu is the expected form after por ke
• aĉetas would sound wrong here
• aĉeti is an infinitive, and por ke is followed by a finite verb, not an infinitive

This -u form is often called the volitive mood. In a sentence like this, it does not mean a command. It is just the normal grammar after por ke.

No. Although the -u ending is also used for commands, that is not what is happening here.

Compare:

• Aĉetu la tekruĉon! = Buy the teapot!
  → command

But in:

• ... por ke mi aĉetu la tekruĉon
  → it is part of a subordinate clause, not an order

Here it means something more like for me to buy or so that I would buy.

Because it is the direct object of aĉetu.

You buy something, and that thing gets the accusative -n:

• mi aĉetu la tekruĉon = I buy the teapot

So:

• tekruĉo = teapot
• tekruĉon = teapot as the direct object

It is a compound word:

• te- = tea
• kruĉo = jug, pot, pitcher

So tekruĉo literally means something like tea-pot or tea-jug, i.e. teapot.

In Esperanto compounds, roots are often joined directly without keeping the final -o of the first noun.

Not if you want to keep the idea for me to buy with an explicit subject mi.

In Esperanto:

• por + infinitive is used when no separate subject is stated
• por ke + verb in -u is used when you have a full clause with its own subject

So:

• por ke mi aĉetu = for me to buy

That is why the sentence does not say por mi aĉeti in the English way.

It is grammatically understandable, but it may sound a little unusual depending on context.

A learner may wonder this because the subject is fendeto (small crack), so the sentence literally centers the crack: The small crack is too big for me to buy the teapot.

That can work, but in real usage many speakers might prefer a sentence focused on the teapot, for example:

• La tekruĉo havas tro grandan fendeton por ke mi aĉetu ĝin.
  = The teapot has too big a crack for me to buy it.

Also, if a particular crack is meant, La fendeto may sound more natural than just Fendeto.

Not absolutely, but many writers do put one before subordinate clauses for clarity.

So both of these are possible:

• Fendeto estas tro granda por ke mi aĉetu la tekruĉon.
• Fendeto estas tro granda, por ke mi aĉetu la tekruĉon.

In short sentences like this, leaving the comma out is common and perfectly acceptable.