Pozvi prosím sestru na sobotní večeři.

Czech uses a special imperative form for commands and requests, just like English uses invite! instead of to invite.

• pozvat = infinitive (to invite)
• pozvi = imperative, 2nd person singular, informal ty

So pozvi means (you) invite! addressed to one person you speak to as ty (a friend, sibling, etc.).

For speaking to more than one person or to someone formally (vy), the imperative is:

• pozvěte – Pozvěte prosím sestru…

Prosím literally comes from the verb prosit (to ask, to beg; prosím = I ask / I beg), but in everyday speech it works like English please.

In this sentence it’s a politeness softener for the imperative:

• Pozvi prosím sestru… ≈ Please invite (your) sister…

You can move prosím to several positions without changing the meaning much:

• Prosím, pozvi sestru na sobotní večeři.
• Pozvi sestru na sobotní večeři, prosím.

All are natural. Putting prosím at the beginning or end often sounds slightly softer.

In Czech, subject pronouns are usually dropped because the verb ending already shows the person.

• pozvi already tells us it is you (ty).
• Saying Ty pozvi prosím sestru… is possible but sounds strongly emphatic, almost like You, invite your sister (not someone else)!

So the neutral, normal command is just Pozvi prosím sestru…

Czech marks grammatical case on nouns. Here, sestra (sister) is the direct object of pozvat (invite), so it must be in the accusative case.

Declension (singular):

• Nominative (dictionary form): sestra – subject
• Accusative (object): sestru – after pozvat (invite someone)

Because we are inviting whom? – sestru, the accusative form is required.

In Czech, possessive pronouns with close family members are often omitted when the possessor is obvious from context.

So:

• Pozvi prosím sestru…
  is normally understood as Invite your sister, please, not Invite (some random) sister.

If you want to be explicit, you can say:

• Pozvi prosím svoji sestru. (your own sister – when you are the subject)
• Pozvi prosím tvoji sestru. (also correct, a bit more explicit/contrasty)

Both structures are possible, but the nuance is a bit different.

• na sobotní večeři – treats the dinner as a specific event, the Saturday dinner (maybe a planned or special one).
• na večeři v sobotu – focuses more on time: a dinner that happens to be on Saturday.

So:

• Pozvi prosím sestru na sobotní večeři.
  ≈ Invite her to the Saturday dinner (the one we already have in mind).

You could also say:

• Pozvi prosím sestru na večeři v sobotu.
  ≈ Invite her for dinner on Saturday (more neutral about what kind of dinner it is).

Again this is about case. The preposition na here takes the accusative because it expresses destination / goal (to, for an event).

The noun večeře (dinner) in the singular:

• Nominative: večeře (subject; dictionary form)
• Accusative: večeři (object or after na meaning to/for an event)

Since we have na co? – na sobotní večeři, we need the accusative večeři.

sobotní is an adjective meaning Saturday or Saturday’s (like Sunday lunch in English).

It belongs to the -í adjective type (like rodinní, osobní), which has the same form for all genders in the singular nominative and accusative.

Here it agrees with večeři (feminine, accusative singular), but its form stays:

• feminine accusative singular: sobotní večeři

So it doesn’t change shape; the case and gender agreement are shown only by večeři, not by sobotní.

zvat and pozvat form an aspect pair:

• zvat – imperfective (to be inviting, to invite repeatedly / in general)
• pozvat – perfective (to invite once, with focus on the result: the invitation is made)

For a single, concrete action – invite her (once) for that dinner – Czech normally uses the perfective imperative:

• Pozvi sestru… – Make sure she ends up invited.

Zvi sestru… would sound like Keep inviting your sister… / Invite your sister regularly, so it is not appropriate for a one‑off Saturday dinner.

Pozvi prosím sestru na sobotní večeři. is:

• Informal (because of pozvi – ty-form)
• Polite in tone (because of prosím)

You say it to:

• friends
• family
• people you address as ty

To speak formally (to vy), you change the verb:

• Pozvěte prosím sestru na sobotní večeři.

Optionally add a possessive for clarity:

• Pozvěte prosím svou/svoji sestru na sobotní večeři.
• Pozvěte prosím vaši sestru na sobotní večeři.

Word order in Czech is more flexible than in English, especially for elements like prosím.

All of these are acceptable:

• Pozvi prosím sestru na sobotní večeři.
• Prosím, pozvi sestru na sobotní večeři.
• Pozvi sestru na sobotní večeři, prosím.
• Pozvi sestru prosím na sobotní večeři. (a bit less common, but still ok)

The basic skeleton Pozvi sestru na sobotní večeři should stay in that order; moving prosím around mainly affects rhythm and slight emphasis, not meaning.

Key points:

• In Czech, stress is always on the first syllable of each word:
  • PO-zvi PRO-sím SES-tru na SO-bot-ní VE-če-ři
• Vowels with accents are long:
  • í in prosím, sobotní, večeři
• r in sestru, večeři is trilled, not like English r.
• č in večeři is like ch in church.

So you get a rhythm like: PO-zvi PRO-sím SES-tru na SO-bot-ní VE-če-ři, with each word starting strongly on its first syllable.