Learn Hardcore Polish: Kiedyś byli szczęśliwą parą, ale dwa lata temu rozstali się. - They once were a happy couple, but two years ago they broke up.

So here it refers to an unspecified time in the past, not a specific moment and not the future. Context (plus the past tense byli) makes it clearly past, not “someday” in the future.

Why is it byli, and not some other form like był or była?

Byli is the past tense, 3rd person plural, masculine-personal form of być (to be).

byłem / byłam – I was (m / f)
byłeś / byłaś – you were (sg, m / f)
był – he was
była – she was
było – it was
byli – they were (group including at least one male)
były – they were (all-female group or non‑personal)

Here “they” is a couple (man + woman), so Polish grammar treats this as masculine personal plural, therefore byli.

If it were two women, you would say Kiedyś były szczęśliwą parą.

Why is it szczęśliwą parą and not szczęśliwa para?

This is about case and agreement.

After the verb być (to be), when you describe what someone is (a profession, role, or state), Polish usually uses the instrumental case.
para (a pair / a couple) in the instrumental singular is:
- parą (ending ‑ą)
The adjective has to agree with the noun in gender, number, and case:
- feminine, singular, instrumental: szczęśliwą

So:

Nominative (dictionary form): szczęśliwa para – a happy couple
Instrumental (needed after “byli”): szczęśliwą parą – (as) a happy couple

That’s why the sentence uses szczęśliwą parą, not szczęśliwa para.

What case is szczęśliwą parą, and when do we normally use that case?

Szczęśliwą parą is in the instrumental singular:

para → parą
szczęśliwa → szczęśliwą

Common uses of the instrumental case:

After być (to be) to say what someone is:
- Ona jest lekarką. – She is a doctor.
- Byli szczęśliwą parą. – They were a happy couple.
With some prepositions (e.g. z in the sense “with”):
- z przyjacielem – with a friend
To express means / tool (often without a preposition):
- pisać długopisem – to write with a pen

In this sentence, it’s the “after być” pattern.

Why is there a comma before ale?

In Polish, you must put a comma before ale when it connects two clauses:

[Kiedyś byli szczęśliwą parą], ale [dwa lata temu rozstali się].

Each part has its own verb (byli, rozstali się), so they are two separate clauses.
Rule: comma + ale + clause is standard here, similar to “..., but ...” in English.

What does dwa lata temu literally mean, and why is it not some other case?

Literally, dwa lata temu is:

dwa – two
lata – years (this is the special form used with 2–4: dwa/trzy/cztery lata)
temu – ago

It functions like “two years ago”.

Structure to remember:

dwa / trzy / cztery lata temu – two / three / four years ago
pięć lat temu – five years ago (after 5+ we use lat, not lata)

There is another, more formal way: przed dwoma laty (literally “before two years”), but dwa lata temu is the most common everyday form.

Why is it rozstali się and not just rozstali? What does się do?

Rozstać się is a reflexive verb meaning “to break up / to part (as a couple)”.

rozstać without się is not used in this sense.
The reflexive pronoun się is part of the verb’s basic form: rozstać się.

So in past tense, 3rd person plural:

rozstali się – they broke up

The się:

often indicates a reflexive or reciprocal action (“they did this to each other”)
is written as a separate word
usually goes right after the verb or after the first stressed element of the verb phrase

You can change word order (e.g. Dwa lata temu się rozstali), but you cannot drop się when you want to say “they broke up”.

Why is it rozstali and not rozstały?

Polish past tense has different plural endings depending on the gender/composition of the group:

rozstali – masculine personal plural
(group with at least one man: “oni”)
rozstały – non‑masculine-personal plural
(all women, or things, animals: “one”)

A romantic couple is typically man + woman, so Polish grammar uses oni → rozstali.

If the couple were two women, the sentence would be:

Kiedyś były szczęśliwą parą, ale dwa lata temu rozstały się.

What is the aspect of rozstali się, and how is it different from rozstawali się?

Rozstali się comes from rozstać się – a perfective verb.

rozstać się (perfective) – to break up (seen as one completed event)
rozstawać się (imperfective) – to be breaking up / to separate (repeatedly, or focusing on the process)

In this sentence, dwa lata temu rozstali się:

We’re talking about one completed breakup at a specific time in the past.
That’s why the perfective rozstali się is used.

Examples:

Oni często się rozstawali i schodzili znowu.
They kept breaking up and getting back together. (imperfective, repeated)
W końcu się rozstali na zawsze.
In the end, they broke up for good. (perfective, single completed event)

Can the word order change? For example, can I say Dwa lata temu rozstali się at the beginning?

Yes, Polish word order is quite flexible, especially for adverbs of time and place. All of these are correct (with slightly different emphasis):

Kiedyś byli szczęśliwą parą, ale dwa lata temu rozstali się.
Kiedyś byli szczęśliwą parą, ale rozstali się dwa lata temu.
Dwa lata temu rozstali się. Kiedyś byli szczęśliwą parą. (two sentences)

Usual patterns:

time – verb – subject or subject – verb – time are very common.
Moving dwa lata temu changes what you highlight, not the basic meaning.

The original order sounds very natural and neutral.

Can kiedyś be placed later in the sentence, and does that change the meaning?

Yes, it can move:

Kiedyś byli szczęśliwą parą... (default, very natural)
Byli kiedyś szczęśliwą parą...
Byli szczęśliwą parą kiedyś... (possible, sounds like you’re slightly stressing “back then / in those days”)

The core meaning (at some time in the past) stays the same.
Putting kiedyś at the very beginning is the most neutral and common in storytelling.

Why is there no explicit word for “they” (like oni) in the sentence?

In Polish, the subject pronoun (ja, ty, on, ona, my, wy, oni, one) is often omitted because:

The verb ending already shows person and number (and often gender).

Here:

byli → 3rd person plural, masculine personal → “they (oni)”
rozstali się → 3rd person plural, masculine personal → “they (oni)”

So “they” is understood from the verb forms.
You could say Oni kiedyś byli szczęśliwą parą, but adding oni is usually only for emphasis or contrast, not required.

Does para always mean a romantic couple, or can it mean other things too?

Para is a general noun meaning “a pair / a couple”. Context decides whether it’s romantic.

Uses:

Romantic couple (very common):
- Są ładną parą. – They’re a nice couple.
Any two people together:
- para przyjaciół – a pair of friends
Two of something:
- para butów – a pair of shoes
- para skarpetek – a pair of socks

In szczęśliwą parą with past context of breaking up, it is naturally understood as a romantic couple.

How is szczęśliwą pronounced, especially the szcz part and the nasal ą?

Key points:

szcz is two consonant sounds [ʂt͡ʂ] (similar to “shch” in fresh cheese said quickly):
- sz – like English “sh” but slightly harder and further back
- cz – like “ch” in chair
- Together: szczę- ~ “sh-chE-” (but blended as one cluster)
ę in szczę- is a nasal vowel; in normal speech it may sound close to “e” with a bit of nasalization.
ś in szczęśliwą is soft, like “sh” but more palatal (tongue closer to y position).
ą at the end (‑wą) is a nasal vowel similar to French “on” in bon, but often in casual speech it can sound close to ‑om:
- szczęśliwą ~ “sh-chesh-LEE-von / -vom”

Stress is on the second-to-last syllable:
szczę‑ŚLI‑wą.