Learn Hardcore Polish: Wolontariusz wyjeżdża na urlop w lipcu. - The volunteer is leaving on vacation in July.

In Polish, the present tense of an imperfective verb (here: wyjeżdżać) is often used for planned or scheduled future events.
So wyjeżdża can mean:

“is leaving / is going away (now)” or
“is going away / will go (at a known time in the future).”

In this sentence the time expression w lipcu makes it clear that we’re talking about the future, not the present.

Could we say Wolontariusz wyjedzie na urlop w lipcu instead? What’s the difference?

Yes, Wolontariusz wyjedzie na urlop w lipcu is also correct.

wyjeżdża (imperfective) – sounds more like a planned, scheduled event; it can feel a bit more neutral or descriptive.
wyjedzie (perfective) – focuses more on the single completed act of leaving; it can sound a bit more definite or factual, especially if you’re stating a decision or prediction.

Both can translate as “The volunteer will go on leave in July,” but the aspectual nuance is slightly different.

What exactly is the difference between urlop and wakacje?

urlop = leave from work or service (paid vacation, military leave, etc.). It implies an official break granted by an employer or institution.
wakacje = holidays/vacation time, especially school or university holidays, or a more general “vacation” feeling.

So someone with a job usually has urlop, and schoolchildren/students have wakacje.

Why do we say na urlop and not w urlopie or do urlopu?

The phrase na urlop is an idiomatic fixed expression meaning “on leave / on vacation.”
Polish often uses na + accusative for going to certain activities or states:

na urlop (on leave)
na obiad (for lunch)
na spotkanie (to a meeting)

So you just have to learn na urlop as the standard collocation. w urlopie and do urlopu are not used in this meaning.

What case is urlop in, and why doesn’t its form change?

After na with a sense of motion (“onto / into / for”), Polish uses the accusative case.
urlop is a masculine inanimate noun and its accusative singular form is the same as the nominative:

nominative: urlop
accusative: urlop

So it is inflected, but you don’t see a change in form.

Why is it w lipcu and not w lipiec? What case is that?

The phrase w lipcu uses the locative case, because after w meaning “in (time/place)” Polish requires the locative.
The noun lipiec (July) declines like this (singular):

nominative: lipiec (dictionary form)
locative: w lipcu

So the change -piec → -pcu is part of the regular declension pattern for some masculine nouns.

Can you show the basic declension of lipiec so I can recognize lipcu?

Singular of lipiec (masculine noun):

Nominative (who? what?): lipiec – Lipiec jest letnim miesiącem.
Genitive (of?): lipca – początek lipca (the beginning of July)
Dative (to/for?): lipcowi – used rarely in practice
Accusative (what?): lipiec – usually same as nominative
Instrumental (with/by?): lipcem – z lipcem (very rare phrase)
Locative (in/on/about?): lipcu – w lipcu (in July)

The key pair you’ll keep meeting is lipiec (subject) vs. w lipcu (time expression).

Is the word order fixed? Could I say W lipcu wolontariusz wyjeżdża na urlop?

Yes, word order in Polish is relatively flexible.
All of these are correct and natural, with slightly different emphasis:

Wolontariusz wyjeżdża na urlop w lipcu. (neutral; focus on the action, then time)
W lipcu wolontariusz wyjeżdża na urlop. (puts emphasis on “in July”)

In most everyday contexts, both versions are fine and mean the same thing.

What exactly does wolontariusz mean? Is it the same as ochotnik?

wolontariusz = a volunteer in an organized setting, e.g. for a charity, NGO, event, hospital, etc. It is a modern, more official term.
ochotnik = more general volunteer, especially someone who volunteers for something dangerous or serious (like the army) or just steps forward on their own.

In the context of NGOs, social work, or charity events, wolontariusz is the standard word.

How do you say “female volunteer”? Is wolontariusz only male?

The feminine form is wolontariuszka.

wolontariusz – male volunteer
wolontariuszka – female volunteer

Sometimes wolontariusz can be used generically (like “volunteer” in English), but if you want to be explicit about gender, you use wolontariuszka.

How do you pronounce wolontariusz and wyjeżdża? The spellings look scary.

A rough guide using English-like sounds:

wolontariusz ≈ vo-lon-TAH-ryoosh
- rz is pronounced like ż, similar to the s in measure (the /ʒ/ sound).
wyjeżdża ≈ vih-YEZH-ja (with a kind of zh-j in the middle)
- żdż is a cluster pronounced roughly like zh-j one after another.

In both words, the stress is on the second-to-last syllable: wo-lon-TA-riusz, wy-JE-żdża.

Why isn’t there any word for “the” in this sentence, like “the volunteer”?

Polish does not use articles (a, an, the) at all.
Whether you mean “a volunteer” or “the volunteer” depends on context, not on a separate word.

So Wolontariusz wyjeżdża na urlop w lipcu could mean either:

A volunteer is going on leave in July
or
The volunteer is going on leave in July
depending on what has been mentioned or is obvious from the situation.

Why is it wyjeżdża and not jedzie here? Don’t both mean “go”?

Both verbs involve movement, but they differ in nuance:

jechać / jedzie – to go (by vehicle) towards some place. It emphasizes the trip itself.
wyjeżdżać / wyjeżdża – to leave / go away from some place (it has the prefix wy- “out”).

In wyjeżdża na urlop, the focus is on leaving for leave, i.e. going away from his usual place of work or residence. Jedzie na urlop is possible too and would emphasize the journey a bit more.

Can this sentence describe a regular habit, or only a one-time event?

Yes, it can also describe a habit.
Wolontariusz wyjeżdża na urlop w lipcu can mean:

this specific year: “The volunteer is going on leave in July (this year).”
a repeated pattern: “The volunteer (always) goes on leave in July.”

Whether it’s one-time or habitual depends entirely on context, just like in English with “He goes on vacation in July.”