Learn Hardcore German: Deine Idee ist höchst interessant.

German possessive pronouns (mein, dein, sein, ihr, unser, euer, Ihr) change their ending to match the gender, number, and case of the noun they refer to, not the owner.

The noun here is Idee.
Idee is feminine: die Idee.
It is the subject of the sentence, so it’s in the nominative case.
Feminine nominative after a possessive pronoun takes -e: deine Idee.

So:

dein Vater (masculine nominative)
deine Mutter (feminine nominative)
deine Ideen (plural nominative)

What case is deine Idee, and how can I tell?

Deine Idee is in the nominative case, because it is the subject of the sentence – the thing that “is interesting.”

You can test it by asking:

Who or what is interesting? → Deine Idee.

That “who/what” question usually points to the nominative subject. The verb ist also agrees with a singular subject.

What is the gender of Idee, and how do I know?

Idee is feminine in German:

the dictionary form is die Idee.

You can recognize it in this sentence from the possessive pronoun:

deine Idee → deine is the form used for feminine nominative singular (and for plural, but Idee is clearly singular here).

You just have to learn the gender with the noun: die Idee (f.), der Tisch (m.), das Haus (n.).

Why is Idee capitalized?

In German, all nouns are capitalized, regardless of where they appear in the sentence.

Idee is a noun, so it must be written as Idee, not idee.

Why is it ist and not bist or seid?

The verb here is sein (to be). It is conjugated for the subject, which is Idee (third person singular).

Conjugation of sein in the present tense:

ich bin
du bist
er/sie/es ist
wir sind
ihr seid
sie/Sie sind

Since Idee corresponds to sie (she/it), you use ist:

Deine Idee ist höchst interessant.
→ Your idea is highly interesting.

Why is interessant not interessante or interessanten?

Here, interessant is a predicative adjective, used after the verb sein (to be).

In German:

Adjectives before a noun usually take endings:
eine interessante Idee (an interesting idea)
eine höchst interessante Idee
Adjectives after verbs like sein, werden, bleiben do not take endings:
Die Idee ist interessant.
Deine Idee ist höchst interessant.

So after ist, you use the base form interessant, with no ending.

What exactly does höchst mean here, and how is it different from sehr?

In this sentence, höchst is an intensifying adverb meaning extremely / highly / very:

höchst interessant ≈ extremely interesting, highly interesting

Nuance:

sehr interessant = very interesting (neutral, common)
höchst interessant = stronger, a bit more formal or expressive, often used in written language or polite speech.

So höchst here does not mean “highest” in the literal comparative sense; it’s functioning as an adverb of degree.

Can höchst go somewhere else in the sentence?

In this structure it’s best, and most natural, to keep höchst directly in front of the adjective:

Deine Idee ist höchst interessant. ✓

You would not normally say:

Deine Idee ist interessant höchst. ✗
Deine Idee ist höchst. ✗ (you need an adjective after it)

When höchst is used as an intensifier, it almost always comes immediately before the adjective or participle it modifies:

höchst gefährlich (extremely dangerous)
höchst erfreulich (most gratifying)

Is höchst the same as “at most” (like höchstens)?

No, they are different:

höchst (here) = extremely, highly
- höchst interessant = highly interesting
höchstens = at most, no more than
- Es dauert höchstens 10 Minuten. = It takes at most 10 minutes.

Don’t confuse höchst interessant with höchstens interessant – the latter would sound odd and wouldn’t mean the same thing.

Can I say Ihre Idee ist höchst interessant instead of Deine Idee?

Yes, but it changes the level of formality and possibly the meaning:

Deine Idee = your idea (informal du; friends, family, people you’re on a first-name basis with)
Ihre Idee (capital I) = your idea (formal Sie; polite form, strangers, professional context)
ihre Idee (lowercase i) = her idea or their idea, depending on context

So to say formally “Your idea is highly interesting,” you’d write:

Ihre Idee ist höchst interessant.

Is the word order the same as in English, or is there anything special about it?

The word order here is basically the same as in English:

Deine Idee (subject)
ist (verb)
höchst interessant (predicate / complement)

This is the standard S–V–(complement) structure for a simple main clause with sein. Nothing tricky here: German and English line up nicely in this type of sentence.

How do you pronounce höchst and Idee?

Approximate pronunciation:

deine → [ˈdaɪ̯nə] (like DIE-nuh)
Idee → [iˈdeː] (ee-DAY, with a long ee sound at the end)
höchst → commonly [høːkst] or [høːçst]
- ö like the vowel in French deux or similar to saying English “eh” while rounding your lips
- final -chst is a cluster; many speakers effectively say it close to /kst/.

So a rough English-friendly approximation would be: “DOY-nuh i-DAY ist HURKST interes-SANT”, though the German vowels are more precise than that.

Could I say Deine Idee ist sehr interessant instead? Is there a difference?

Yes, you can say:

Deine Idee ist sehr interessant.

This is perfectly natural and common. The difference is mainly nuance:

sehr interessant = very interesting (neutral, everyday)
höchst interessant = extremely / highly interesting (stronger, somewhat more formal or emphatic)

Both are positive; höchst just sounds a bit more intensified and sometimes more polite/formal.