Learn Hardcore Polish: Budzik budzi dzieci o siódmej rano. - The alarm clock wakes the children at seven in the morning.

In the sentence Budzik budzi dzieci o siódmej rano, the subject is budzik (the alarm clock), which is 3rd person singular.
So the correct form is budzi (it wakes), not budzę (I wake) or budzisz (you wake).

If there are many children, why is the verb budzi (singular) and not budzą (plural)?

The verb agrees with the subject, not with the object.

Budzik budzi dzieci. – budzik is the subject (one alarm clock) → budzi (3rd person singular).
Dzieci budzą się o siódmej. – dzieci is the subject (children) → budzą (3rd person plural).

In Budzik budzi dzieci, dzieci is the object (the thing being woken), so it does not control the verb form. Only budzik does.

What is the difference between budzik and budzi?

They are different parts of speech:

budzik – a noun, meaning alarm clock.
budzi – a verb form, 3rd person singular present of budzić (to wake).

So, literally:

Budzik – alarm clock
budzi – wakes

The sentence structure is: [alarm clock] [wakes] [children] [at seven in the morning].

Why is dzieci used, and what case is it in?

Dzieci is the plural of dziecko (child). It is an irregular plural:

1 child – dziecko
2/3/4 children – dzieci
many children – dzieci

In the sentence Budzik budzi dzieci, dzieci is the direct object of the verb budzi, so it is in the accusative plural.

For this noun, nominative plural and accusative plural look the same (dzieci), so you tell the case from the sentence role, not from the form.

Why is there no word for the or an before budzik or dzieci?

Polish has no articles like English a/an or the.

budzik can mean a(n) alarm clock or the alarm clock, depending on context.
dzieci can mean children, the children, or some children, again depending on context.

So Budzik budzi dzieci can be translated as:

The alarm clock wakes the children.
An alarm clock wakes children.

The exact English article choice is decided by context, not by separate words in Polish.

What does o siódmej literally mean, and why does siódmej end in -ej?

o siódmej means at seven (o’clock).

o is a preposition often used with time expressions → it requires the locative case.
siódmej is the locative singular feminine form of siódma (seventh).

Why feminine? Because it agrees with an implied noun:

o siódmej (godzinie) = at the seventh (hour) → at seven o’clock.

Godzina (hour) is feminine, so the ordinal number siódma takes the feminine locative form siódmej after o.

Why do we say o siódmej, not w siódmej or na siódmą?

For clock time, the normal preposition is o:

o pierwszej – at one
o trzeciej – at three
o siódmej – at seven

w is used with days, months, years, or locations:

w poniedziałek – on Monday
w maju – in May
w 2020 roku – in 2020

na siódmą is also possible but means for seven o’clock, focusing on the intended time / deadline (e.g. Przyjdź na siódmą – Come for seven o’clock).

In Budzik budzi dzieci o siódmej rano, we are just saying at seven in the morning, so o is correct.

What exactly is rano? Is it a noun, and can it be left out?

Rano is used like an adverb meaning in the morning.

In dictionaries you will often see it listed as an indeclinable noun/adverbial, but practically, you can treat it like an adverb that does not change form.

In time expressions:

rano – in the morning
po południu – in the afternoon
wieczorem – in the evening
w nocy – at night

You can say:

Budzik budzi dzieci o siódmej. – The alarm clock wakes the children at seven.
Budzik budzi dzieci o siódmej rano. – … at seven in the morning.

Rano is optional here; it just clarifies that we mean morning, not evening.

How would I say at seven in the evening instead of in the morning?

You keep the structure and change only the time-of-day word:

o siódmej rano – at seven in the morning
o siódmej wieczorem – at seven in the evening

So you could say:

Budzik budzi dzieci o siódmej wieczorem. – The alarm clock wakes the children at seven in the evening.

(Grammatically fine, though in real life you’d more likely talk about morning.)

What is the difference between budzi and obudzi?

Both come from related verbs:

budzić (imperfective) → budzi (wakes / is waking, habitually or repeatedly)
obudzić (perfective) → obudzi (will wake, or wakes once, as a single completed event)

Typical use:

Budzik budzi dzieci o siódmej rano.
The alarm clock wakes the children at seven in the morning.
→ general, repeated, habitual action (every day).
Budzik obudzi dzieci o siódmej rano.
The alarm clock will wake the children at seven in the morning.
→ a single future event, or a specific occasion.

So budzi = ongoing / habitual; obudzi = one completed act (often future).

Can the word order change, or must it be Budzik budzi dzieci o siódmej rano?

Polish has relatively flexible word order, especially in simple sentences. All of these are grammatically correct:

Budzik budzi dzieci o siódmej rano.
Budzik o siódmej rano budzi dzieci.
O siódmej rano budzik budzi dzieci.
Dzieci budzik budzi o siódmej rano. (more marked / emphatic)

The basic, neutral order with subject–verb–object is:

Budzik budzi dzieci o siódmej rano.

Changing the order usually adds emphasis (for example, putting o siódmej rano at the start emphasizes the time).

How would I say The children wake up at seven in the morning (without mentioning the alarm clock)?

You make dzieci the subject and use the reflexive form of the verb:

Dzieci budzą się o siódmej rano.
= The children wake up at seven in the morning.

Breakdown:

dzieci – children (subject)
budzą – they wake (3rd person plural)
się – reflexive particle → wake themselves / wake up
o siódmej rano – at seven in the morning

Compare:

Budzik budzi dzieci o siódmej rano. – The alarm clock wakes the children…
Dzieci budzą się o siódmej rano. – The children wake up…

What is the plural of budzik, and how would I say The alarm clocks wake the children at seven in the morning?

Budzik (alarm clock) is a regular masculine noun:

1 budzik – one alarm clock
2/3/4 budziki – two/three/four alarm clocks
5+ budzików – five (or more) alarm clocks

To say The alarm clocks wake the children at seven in the morning, you make budziki the subject and use a plural verb:

Budziki budzą dzieci o siódmej rano.

Here:

budziki – alarm clocks (subject, plural)
budzą – they wake (3rd person plural)
dzieci – children (object, accusative plural)
o siódmej rano – at seven in the morning.