In short

The conditional (tryb przypuszczający) is Polish for “would (do)” - what you would do, could do, or would like. It is not a new set of forms to memorise: you take the past-tense l-participle you already know (Lesson 21), add the little particle by, and glue on the same mobile personal endings as the past. So czytał (he read) -> czytałby (he would read), czytałem (I read) -> czytałbym (I would read). Because it reuses the l-form, the conditional still agrees with gender and splits virile / non-virile in the plural.

The rule

The conditional has three ingredients stacked in a fixed order:

l-participle + by + personal ending

The l-participle is exactly the gendered past form (-ł / -ła / -ło / -li / -ły). The by is invariable. The personal ending is the past-tense clitic -m / -ś / (nothing) / -śmy / -ście, and it lands on by, never on the participle:

• 1sg byłbym = był + by + m (not byłembym)
• 2sg byłbyś = był + by + ś
• 3sg byłby = był + by (no ending)
• 1pl bylibyśmy = byli + by + śmy
• 2pl bylibyście = byli + by + ście
• 3pl byliby = byli + by (no ending)

It is the past form, so gender still shows

Because the conditional is built on the l-participle, a man and a woman say it differently, just as in the past: a man says chciałbym, a woman says chciałabym (I would like). The plural keeps the virile vs non-virile contrast (Lesson 30): oni zrobiliby (a group with a man) versus one zrobiłyby (women/things).

The mobile “by”: it can jump onto a conjunction

Like the past-tense endings, by (with its personal ending) is a clitic and does not have to sit on the verb. In the neutral order it stays on the l-form (Chętnie bym poszedł, Poszedłbym chętnie), but it very often detaches and hops onto an earlier word - a conjunction or a question word - which then absorbs both by and the personal ending:

• że + by + m -> żebym, aby + m -> abym, gdy + by + m -> gdybym
• co -> co by / cobym, kto -> kto by, jak -> jak by

This is why the introducing words of purpose and unreal-if clauses look the way they do: żeby, aby, gdyby are literally conjunction + by, and they still carry the personal ending (żebyś, żebyśmy, gdybyś, gdybyśmy). One firm rule carried over from the past tense: the by never attaches to the negation nie - write nie zrobiłbym, not niebym zrobił.

What the conditional is used for

• Politeness / softening - the everyday core. Chciałbym… (I would like) is far softer than Chcę…; Czy mógłbyś…? (Could you…?) softens a request.
• Wishes and cautious statements: Wolałbym zostać. (I would rather stay.) To byłby dobry pomysł. (That would be a good idea.)
• Purpose clauses with żeby / aby (“so that, in order to”): when the two clauses have different subjects, żeby takes the conditional (Powiedz mu, żeby przyszedł - Tell him to come); with the same subject żeby takes a bare infinitive (Przyszedłem, żeby ci pomóc - I came to help you).
• Unreal conditions with gdyby (“if…”): Gdybym miał czas, poszedłbym. (If I had time, I would go.) Both clauses take the conditional. This is developed fully in Lesson 51.

Forms & patterns

How the three pieces combine (personal ending sits on by, not on the participle):

Full paradigm - regular czytać (to read, imperfective) = “would read”:

The verb być (to be) = “would be” - the model for all forms:

A perfective verb - zrobić (to do/get done) = “would do”: same endings; aspect gives the “one-off, completed” reading.

Modal móc (can) = “could” - watch the ó/o shift inherited from the past l-form:

Conjunction + by fusions (the personal ending rides along):

Examples

Common mistakes

• byłembym / czytałembym -> byłbym / czytałbym - the personal ending goes on by, not on the l-form. You never write the past ending twice.
• ja chciałbym said by a woman -> chciałabym - the l-participle still matches your own gender.
• oni zrobiłyby (group with a man) -> zrobiliby - a group including a male is virile: -li before by.
• niebym poszedł / nie bym poszedł -> nie poszedłbym - by never attaches to nie; keep it on the verb.
• Gdybym miałbym czas -> Gdybym miał czas - do not double the by: once it is in gdyby, the verb of that clause drops its own by (the l-form stays plain: miał).
• Chcę stolik przy oknie (to a waiter) -> Chciałbym stolik przy oknie - the plain present sounds blunt; the conditional is the polite form.
• Powiedz mu, że przyszedł (meaning “tell him to come”) -> Powiedz mu, żeby przyszedł - a purpose/command clause needs żeby + conditional, not plain że.

Tips

• One recipe covers every verb: past l-form + by + past personal ending. If you can build the past tense, the conditional is almost free.
• The ending always rides on by: -bym, -byś, -by, -byśmy, -byście, -by. Say them as a block, like a mini-conjugation.
• Learn three politeness formulas as ready-made phrases: chciałbym / chciałabym (I’d like), czy mógłbyś / mogłabyś (could you), wolałbym / wolałabym (I’d rather).
• żeby, aby, gdyby already contain by - so the verb inside those clauses keeps a plain l-form (gdybym miał), it does not add a second by.
• Same subject -> żeby + infinitive (żeby pomóc); different subject -> żeby + conditional (żeby pomógł). This one test settles most żeby clauses.
• Remember the plural test from the past: is there a male human in the group? Yes -> -liby; no -> -łyby.