Learn Hardcore Esperanto: Mi longe pensas pri bona donaco, ĉar por mi ŝia naskiĝtago estas tre grava. - I think for a long time about a good present, because for me her birthday is very important.

longa = long (adjective)
- longa vojo = a long road
longe = for a long time / at a great distance (adverb)
- Mi longe pensas = I think for a long time
- Li loĝas longe de mi = He lives far from me

In this sentence, longe tells us about the duration of the thinking, so it’s “I think for a long time about a good present.”

Could I say Mi pensas longe pri bona donaco instead of Mi longe pensas…? Is the word order important?

Both Mi longe pensas pri bona donaco and Mi pensas longe pri bona donaco are grammatically correct.

Esperanto word order is fairly flexible. The differences are:

Mi longe pensas pri bona donaco
Mild emphasis on the duration of the thinking: “I think for a long time about a good present.”
Mi pensas longe pri bona donaco
Very similar meaning; some speakers feel this sounds slightly more “neutral,” with pensas remaining close to its subject Mi.

Neither is wrong. In practice, adverbs like longe, multe, ofte, ĉiam quite often come before the verb, as in the original sentence.

Why is it pensas pri bona donaco and not something like pensas bonan donacon without pri?

In Esperanto, pensi almost always takes the preposition pri when you mean “to think about” something.

pensi pri io = to think about something
- Mi pensas pri bona donaco. = I’m thinking about a good present.

If you say pensi ion, it usually has a different meaning, more like “to have an opinion about something”:

Kion vi pensas pri li? = What do you think about him?
(You wouldn’t say pensas lin here.)

So for “think about a present,” the natural pattern is pensi pri donaco, not pensi donacon.

Why is it bona donaco and not bonan donacon? Shouldn’t the object get -n?

You only add -n (the accusative) to direct objects, not to nouns that follow a preposition.

Here, donaco is not a direct object of pensas; it is the object of the preposition pri:

Verb: pensas
Preposition: pri
Object of the preposition: bona donaco

Objects of prepositions don’t get -n, so:

Mi pensas pri bona donaco. ✅
Mi pensas pri bonan donacon. ❌ (ungrammatical)

If you had a direct object without a preposition, then you would use -n:

Mi havas bonan donacon. = I have a good present.

There’s no word for “a” or “the” before bona donaco. How do we know if it’s “a good present” or “the good present”? Why is there no article?

Esperanto only has one article: la (roughly “the”). There is no separate word for “a”.

So:

bona donaco can correspond to English “a good present” or just “good present”, depending on context.
la bona donaco = the good present (a specific one you both know about)

In this sentence, we’re talking about some appropriate present in general, not one already known or specified, so no article is used:

Mi pensas pri bona donaco. = I’m thinking about a good present.

Using la here (pri la bona donaco) would suggest a specific present that both speaker and listener already know about.

Why is it ŝia naskiĝtago instead of something like la naskiĝtago de ŝi?

Esperanto normally uses possessive adjectives (ending in -a) rather than de + pronoun for possession:

ŝia naskiĝtago = her birthday
mia libro = my book
via amiko = your friend

You can say la naskiĝtago de ŝi, but:

It’s much less natural in this everyday context.
It tends to feel more heavy or emphatic (like “the birthday of her” in English).

So ŝia naskiĝtago is the normal, simple way to say “her birthday.”

Why is there no la before ŝia naskiĝtago? Shouldn’t it be la ŝia naskiĝtago?

When a noun already has a possessive adjective (mia, via, lia, ŝia, nia, via, ilia), you normally don’t use la as well:

ŝia naskiĝtago = her birthday
mia domo = my house
ilia infano = their child

Adding la in front of a possessive is usually unnecessary or stylistically marked. So:

ŝia naskiĝtago ✅ (normal)
la ŝia naskiĝtago ❌ (not used in this sense)

Why does the sentence use ĉar? Does ĉar change the word order like “because” sometimes does in English?

Ĉar is the normal conjunction for “because”.

Unlike in English, ĉar does not cause any special word order change. Esperanto keeps the standard order (usually Subject–Verb–Object or complement) in subordinate clauses:

Ĉar por mi ŝia naskiĝtago estas tre grava.
- Subject: ŝia naskiĝtago
- Verb: estas
- Complement: tre grava
- And por mi is a prepositional phrase showing “for me / to me.”

You can move the ĉar-clause around in the sentence for style:

Ĉar por mi ŝia naskiĝtago estas tre grava, mi longe pensas pri bona donaco.
Mi longe pensas pri bona donaco, ĉar por mi ŝia naskiĝtago estas tre grava.

Both are correct, and the word order inside the ĉar-clause stays normal.

What is the difference between pri and por in this sentence?

They have different core meanings and roles:

pri = about, concerning, regarding
- pensi pri bona donaco = to think about a good present
por = for, for the benefit of, for (someone’s sake / purpose)
- por mi = for me / as far as I’m concerned / to me

In the sentence:

Mi longe pensas pri bona donaco
→ “I’ve been thinking for a long time about a good present.”
ĉar por mi ŝia naskiĝtago estas tre grava
→ “because for me her birthday is very important.”

Using pri mi here would mean “about me,” which would change the meaning completely.

Why is it estas tre grava and not estas tre grave?

Grava is an adjective (“important”), and grave is an adverb (“seriously / gravely / importantly” in some contexts).

In this sentence, we are describing the birthday itself, which is a noun, so we need an adjective:

ŝia naskiĝtago estas tre grava
= her birthday is very important.
(grava agrees with naskiĝtago, a noun.)

Grave (adverb) would modify a verb or an entire statement, not the noun directly. For example:

Li parolis grave. = He spoke seriously.
Estas grave veni ĝustatempe. = It is serious / important to come on time.

So here, grava is the correct form.

Could I say ŝia naskiĝtago tre gravas por mi instead of estas tre grava?

Yes, ŝia naskiĝtago tre gravas por mi is also correct and natural.

Two patterns:

estas + adjective
- ŝia naskiĝtago estas tre grava por mi
  → “her birthday is very important for me.”
verb form of the adjective: gravas
- ŝia naskiĝtago tre gravas por mi
  → literally “her birthday very matters / is important to me.”

Nuance:

estas grava presents “important” clearly as a property of the birthday.
gravas por mi puts a bit more emphasis on the fact that it matters to me.

Both are widely used; in everyday speech they are very close in meaning.

How does por mi work here? Is it like “for me” or “to me,” and is it really necessary?

Por mi literally means “for me”, but in this context it functions like English “for me / to me / in my opinion / from my point of view.”

ŝia naskiĝtago estas tre grava
= her birthday is very important (as a general statement).
ŝia naskiĝtago estas tre grava por mi
= her birthday is very important to me personally.

So por mi:

Marks that this is subjective importance (to the speaker).
Softens the statement; it doesn’t claim it’s objectively very important for everyone.

The sentence would still be grammatically correct without por mi, but it would lose that nuance of “for me personally.”

Why is the verb pensas in the simple present? In English we’d probably say “I have been thinking” or “I’ve been thinking for a long time.”

Esperanto’s present tense (-as) is used for both:

Simple present (I think)
Present continuous (I am thinking)
And often even ongoing situations like English “I have been thinking”

The duration is normally shown not by a different tense but by adverbs or time expressions, like longe, jam, delonge, etc.:

Mi longe pensas pri bona donaco.
≈ I’ve been thinking for a long time about a good present.
Mi jam delonge pensas pri tio.
≈ I’ve already been thinking about that for a long time.

So pensas is the normal, expected form here; you don’t need a special tense to match English “have been thinking.”