Dreh den Pfannkuchen bitte um, sonst wird er zu dunkel.

Dreh is the imperative form, used to give a command to du.

The verb is umdrehen = to turn over / flip.

For a du-command, German usually uses the verb stem:

• du drehst = you turn
• Dreh ... um! = Turn ... over!

You may also sometimes see Drehe ... um!, but in everyday German, Dreh is much more common.

So:

• Dreh den Pfannkuchen um! = Flip the pancake over!

Because umdrehen is a separable verb.

Its two parts are:

• drehen = to turn
• um- = over / around

In many normal sentence patterns, separable prefixes move to the end:

• Ich drehe den Pfannkuchen um.
• Dreh den Pfannkuchen bitte um.

So the full verb is still umdrehen, but in this sentence it appears split into:

• Dreh ... um

This is very common in German with separable verbs, such as:

• aufstehen → Steh auf!
• anmachen → Mach das Licht an!

Because Pfannkuchen is the direct object of the verb, so it is in the accusative case.

The noun Pfannkuchen is masculine:

• nominative: der Pfannkuchen
• accusative: den Pfannkuchen

Here, the command is telling someone to flip the pancake, so the pancake is the thing being acted on. That makes it the direct object.

So:

• der Pfannkuchen = the pancake (subject form)
• den Pfannkuchen = the pancake (object form)

Because er refers back to der Pfannkuchen, which is a masculine noun.

In German, pronouns agree with the grammatical gender of the noun:

• der Pfannkuchen → er
• die Pfanne → sie
• das Messer → es

Also, in this clause, er is the subject, so nominative er is correct.

That is why it is:

• sonst wird er zu dunkel

and not:

• sonst wird ihn zu dunkel (incorrect)

ihn would be accusative, but here the pancake is not the object; it is the subject of wird.

Because German main clauses normally follow the verb-second rule.

Sonst counts as the first element in the clause, so the finite verb must come next:

• Sonst wird er zu dunkel.

Structure:

• Sonst = position 1
• wird = position 2
• er = after the verb

This is the same pattern you see in sentences like:

• Heute gehe ich nach Hause.
• Dann kommt er später.
• Sonst wird er zu dunkel.

If there were no fronted element, you could say:

• Er wird sonst zu dunkel.

That is also possible, but it has a slightly different emphasis.

Here sonst means otherwise.

So the sentence means something like:

• Flip the pancake over, otherwise it will get too dark.

It introduces the consequence of not doing the first action.

Common uses of sonst:

• Beeil dich, sonst verpasst du den Zug.
  Hurry up, otherwise you’ll miss the train.

• Nimm einen Regenschirm mit, sonst wirst du nass.
  Take an umbrella, otherwise you’ll get wet.

Zu dunkel means too dark.

It expresses excess—more dark than is desirable.

• zu dunkel = too dark
• sehr dunkel = very dark

So in this sentence, zu dunkel implies a problem:

• sonst wird er zu dunkel = otherwise it will become too dark

Compare:

• Der Pfannkuchen ist sehr dunkel.
  The pancake is very dark.
  (just a description)

• Der Pfannkuchen ist zu dunkel.
  The pancake is too dark.
  (it has gone past the acceptable point)

Yes. In this sentence, wird is from werden, and it means becomes / gets.

So:

• Er wird dunkel. = It becomes dark / It gets dark.
• Er wird zu dunkel. = It gets too dark.

This use of werden is very common for changes of state:

• Es wird kalt. = It’s getting cold.
• Ich werde müde. = I’m getting tired.
• Die Suppe wird heiß. = The soup is getting hot.

So here it is not a future tense meaning like will in English in a strict grammar sense, even though English often translates it naturally as will get too dark.

Bitte is quite flexible in German. It is often inserted into requests to make them more polite.

Here:

• Dreh den Pfannkuchen bitte um.

That sounds natural and polite.

You could also hear:

• Bitte dreh den Pfannkuchen um.
• Dreh bitte den Pfannkuchen um.

All of these are possible. The version in your sentence is very normal in spoken German.

So bitte does not change the grammar much; it mainly softens the command.

Often yes, but there is an important regional detail.

In much of Germany, Pfannkuchen means pancake.
However, in and around Berlin, Pfannkuchen can mean a jam-filled doughnut (what many other Germans call a Berliner).

So learners sometimes get confused.

In this sentence, because of Dreh ... um and sonst wird er zu dunkel, it clearly means a pancake that is cooking in a pan.

Yes. A common alternative is wenden.

For example:

• Wende den Pfannkuchen!
• Wende den Pfannkuchen bitte!

That also means flip/turn the pancake over.

But umdrehen is very common and very natural in everyday speech. It is often the most straightforward verb for physically turning something over.

So:

• den Pfannkuchen umdrehen = to turn the pancake over
• den Pfannkuchen wenden = to flip/turn the pancake

Both work, but umdrehen may feel slightly more conversational.

It is informal, because the imperative Dreh is the command form for du.

If you were speaking formally to someone, you would use Sie:

• Drehen Sie den Pfannkuchen bitte um, sonst wird er zu dunkel.

So the original sentence is what you would say to:

• a friend
• a family member
• a child
• someone you address as du

Not to someone you speak to as Sie.

Yes, absolutely. It sounds very natural.

It has several features of everyday spoken German:

• a du-imperative: Dreh
• polite softening with bitte
• a very common separable verb: umdrehen
• a practical consequence introduced by sonst

So this is exactly the kind of sentence you might hear in a kitchen:

• Dreh den Pfannkuchen bitte um, sonst wird er zu dunkel.

Natural English would be something like:

• Flip the pancake over, otherwise it’ll get too dark.