Der Verkehr ist heute stark.

Because Verkehr is a masculine noun in German, so its basic article is der.

• der Verkehr = the traffic
• grammatical gender in German is something you usually have to learn with the noun

Here, der Verkehr is in the nominative case because it is the subject of the sentence.

In this sentence, Verkehr means traffic.

It usually refers to traffic on roads, but depending on context, Verkehr can also appear in other meanings, such as:

• public transport / transit
• movement of vehicles
• in other contexts, even interaction or intercourse in older or more formal usage

But in Der Verkehr ist heute stark, the normal meaning is clearly traffic.

Ist is the 3rd person singular form of sein (to be).

So:

• der Verkehr = the traffic
• ist = is
• heute = today
• stark = heavy / intense / strong

German often uses sein + adjective where English also uses to be + adjective:

• Der Verkehr ist stark. = The traffic is heavy.

Yes, stark often means strong, but like many adjectives, it can have different natural translations depending on context.

With Verkehr, stark means something like:

• heavy
• dense
• intense

So Der Verkehr ist heute stark is a natural way to say:

• Traffic is heavy today.

This is a good example of how you should translate by meaning in context, not word-for-word.

Because stark comes after the verb ist and is being used as a predicate adjective.

In German:

• attributive adjective (before a noun) takes an ending
  
  • der starke Verkehr = the heavy traffic
• predicate adjective (after sein, werden, bleiben, etc.) does not take an ending
  
  • Der Verkehr ist stark.

So here stark stays in its basic form.

German word order often places the verb in second position in a main clause.

So in:

• Der Verkehr = position 1
• ist = position 2
• heute = later in the sentence
• stark = final element here

This is a normal sentence pattern.

You can also move heute to the front for emphasis:

• Heute ist der Verkehr stark.

That still means the same thing, but it highlights today more strongly.

Yes, absolutely.

Both are correct:

• Der Verkehr ist heute stark.
• Heute ist der Verkehr stark.

The difference is mainly emphasis:

• Der Verkehr ist heute stark. → neutral statement about the traffic
• Heute ist der Verkehr stark. → puts more focus on today

This kind of word order flexibility is very common in German, as long as the conjugated verb stays in second position in a main clause.

Verkehr is normally treated as a singular mass noun, much like traffic in English.

So German says:

• der Verkehr ist ... = traffic is ...

You usually do not use a plural when talking about traffic in the everyday sense.

German does have a plural form die Verkehre, but that is used in more specialized contexts, for example when talking about different kinds of transport systems or patterns of movement, not ordinary road traffic.

Yes, but the structure changes depending on what you want to say.

You can say:

• Es gibt heute viel Verkehr. = There is a lot of traffic today.
• Der Verkehr ist heute stark. = Traffic is heavy today.

These are similar, but not identical in structure:

• viel Verkehr focuses on a large amount of traffic
• stark describes the traffic as heavy/intense

Both are natural.

Yes. Ist is present tense, and heute simply adds the time meaning today.

So the sentence is literally in the present tense:

• The traffic is heavy today.

German often uses the present tense for things happening now, today, or in the near future, just like English often does.

It is in the nominative case.

That is because der Verkehr is the subject of the sentence—the thing being described.

You can test it by asking:

• What is heavy today?
• The traffic.

So der Verkehr is the subject, and therefore nominative.

A simple pronunciation guide is:

dehr fer-KEHR ist HOY-tuh shtark

A few helpful notes:

• V in Verkehr is pronounced like f here
• kehr sounds roughly like care, but with a German r
• heute sounds roughly like HOY-tuh
• st at the start of stark is usually pronounced sht

A more IPA-style version would be approximately:

[deːɐ̯ fɛɐ̯ˈkeːɐ̯ ɪst ˈhɔʏtə ʃtaʁk]

Yes, if you want to turn it into a noun phrase:

• der starke Verkehr = the heavy traffic

Here stark comes before Verkehr, so it needs an adjective ending:

• stark → starke

Compare:

• Der Verkehr ist stark. = The traffic is heavy.
• Der starke Verkehr nervt. = The heavy traffic is annoying.

So the form changes depending on whether the adjective is:

• after the verb → no ending
• before the noun → takes an ending