Tandnerven er følsom.

Because Danish, like German, very often forms compound nouns by writing them as a single word.

• tand = tooth
• nerve = nerve
• tandnerve = tooth nerve / dental nerve

Then tandnerven means the tooth nerve or the dental nerve.

This is very normal in Danish. English often writes similar ideas as two words, but Danish usually joins them.

The ending -en is the definite article for many common-gender singular nouns in Danish. It means the.

So:

• en tandnerve = a tooth nerve
• tandnerven = the tooth nerve

Unlike English, Danish often puts the at the end of the noun instead of using a separate word before it.

Because in Danish, the definite article is usually attached to the noun itself.

So English:

• the tooth nerve

becomes Danish:

• tandnerven

You do not normally say den tandnerven here. That would usually be wrong in this simple sentence.

A separate word such as den is used in other structures, for example with an adjective:

• den følsomme tandnerve = the sensitive tooth nerve

Er is the present tense of at være, which means to be.

So:

• jeg er = I am
• du er = you are
• tandnerven er = the tooth nerve is

Danish verbs are nice in one way: they do not change for person the way English does. You use er with I, you, he, we, etc. in the present tense.

Følsom is an adjective. It means sensitive.

In this sentence, it comes after er, so it is describing the subject:

• Tandnerven = the tooth nerve
• er følsom = is sensitive

So the whole sentence means that the tooth nerve has the quality of being sensitive.

After er, Danish adjectives are often used in their base form, especially when describing a singular common-gender noun.

Here:

• en tandnerve
• tandnerven
• therefore: følsom

Compare:

• Nerven er følsom. = The nerve is sensitive.

But adjective forms can change in other contexts:

• et følsomt område = a sensitive area
• følsomme tænder = sensitive teeth

So følsom is the correct form here because tandnerven is singular and common gender.

It is an en word.

The base noun is:

• en nerve = a nerve

When nerve is the main part of the compound, the whole compound keeps that gender:

• en tandnerve
• tandnerven

A useful rule: in Danish compounds, the last part usually determines the grammatical gender.

A rough guide for an English speaker is:

• følsom ≈ FURL-sum or FEL-sum, but with a Danish ø sound that does not exist exactly in English

A few notes:

• ø is a rounded front vowel; it can be tricky for English speakers
• the word stress is on the first syllable: FØLsom
• the second syllable is weaker

You do not need a perfect pronunciation right away. The main challenge is the vowel ø.

A rough guide is:

• tandnerven ≈ TAN-ner-ven

Helpful notes:

• the d in tand is often very soft in normal Danish speech, and may sound almost absent to English ears
• the stress is mainly on the first syllable: TANDnerven
• the v in nerven may sound softer than English v

So if you say something close to TAN-ner-ven, people will likely understand you.

Yes, you could say nerven i tanden, which literally means the nerve in the tooth.

But tandnerven is a very natural Danish compound and often the more compact, dictionary-like way to express the idea.

Compare:

• tandnerven = the tooth nerve / dental nerve
• nerven i tanden = the nerve in the tooth

Both can work, but they are not always identical in style:

• tandnerven sounds more like a set term
• nerven i tanden sounds more descriptive

In this sentence, yes, it most naturally means physically sensitive.

But følsom can also mean sensitive in a more emotional or abstract sense, depending on context. For example, a person can be følsom too.

So the word has a broad meaning, just like English sensitive. The noun tandnerven makes the physical meaning obvious here.

The singular forms are:

• en tandnerve = a tooth nerve
• tandnerven = the tooth nerve

The plural forms are:

• tandnerver = tooth nerves
• tandnerverne = the tooth nerves

And the adjective would usually change in plural:

• Tandnerverne er følsomme. = The tooth nerves are sensitive.

Because this is a basic Danish main clause:

• subject
  • verb
    • complement

So:

• Tandnerven = subject
• er = verb
• følsom = complement

This is very similar to English:

• The tooth nerve is sensitive.

Danish word order often feels familiar in simple statements like this.