Learn Hardcore Polish: Moje marzenie to długi spacer w parku.

Polish does not use indefinite or definite articles like a or the. Noun phrases consist of the noun (and any adjectives), and context tells you whether it’s specific or general. So długi spacer can mean a long walk or the long walk, depending on context.

Why is moje used instead of mój or moja?

moje is the neuter nominative singular form of the possessive pronoun meaning my. It matches marzenie, which is a neuter noun. For masculine singular nouns you would use mój, for feminine singular moja, and for non-masculine plurals moje again.

What function does to serve in this sentence?

to here is a linking word used in equative constructions (the X to Y pattern) in Polish. It acts like the verb jest (“is”) but doesn’t change the case of the predicate. So Moje marzenie to długi spacer literally follows “My dream — is a long walk.”

Why is długi spacer in the nominative case and not instrumental?

In sentences with to, both sides of the equation stay in the nominative case. If you replace to with jest, you must switch the predicate to the instrumental:
• Moje marzenie jest długim spacerem.
With to, you keep it as nominative: długi spacer.

Why is w parku used instead of do parku?

w parku indicates location (a walk in the park), while do parku indicates movement toward the park (a walk to the park). Here we want to say the walk takes place inside the park.

Which case does the preposition w require here, and why is park in that form?

When w means “in” (location), it takes the locative case. For inanimate masculine nouns like park, the locative singular ending is -u, so park becomes parku.

Can we replace to with jest, and if so, what changes are needed?

Yes. You get:
Moje marzenie jest długim spacerem w parku.
Here długi spacer changes to the instrumental długim spacerem to agree with jest.

Is it possible to invert the sentence order, like Długi spacer w parku to moje marzenie? Does that affect the meaning?

Yes. Polish has flexible word order. Długi spacer w parku to moje marzenie is perfectly natural. It simply shifts emphasis slightly onto the walk, but the basic meaning (“My dream is a long walk in the park”) remains the same.

What’s the difference between marzenie and sen? They both translate as “dream” in English.

marzenie refers to a wish or aspiration—something you hope or long for. sen refers to the dream you experience while sleeping. So use marzenie for desires and sen for nighttime dreams.

Could I replace marzenie with sen, as in Mój sen to długi spacer w parku?

Although it’s grammatically correct, that sentence would mean “My sleeping dream is a long walk in the park,” i.e. you dreamed about walking while asleep. To express a desire, you need marzenie.