Hun er spontan.

• Hun = she
• er = is (present tense of å være, to be)
• spontan = spontaneous

So the sentence structure is:

subject + verb + adjective

That is very similar to English: She is spontaneous.

Er is the present tense of å være (to be).

Norwegian does not change the verb for different persons the way English does. So you get:

• jeg er = I am
• du er = you are
• hun er = she is
• vi er = we are

So er stays the same no matter who the subject is.

Because spontan is the basic form of the adjective, and that is the form normally used here when talking about a woman or a man:

• Hun er spontan.
• Han er spontan.

The form spontant is the neuter form, used with a neuter noun or sometimes with det:

• et spontant svar = a spontaneous answer
• Det var spontant. = That was spontaneous.

So for hun, spontan is correct.

Normally, no.

If you are describing she, you say:

• Hun er spontan.

Spontant would sound wrong here because it is the neuter form of the adjective, not the form used for a female person.

Because spontan is a predicate adjective here: it comes after er and describes the subject.

In Norwegian, you do not use an article before an adjective in this kind of sentence.

So:

• Hun er spontan. = correct
• Hun er en spontan. = incorrect

But if the adjective comes before a noun, then you can have an article:

• Hun er en spontan person. = She is a spontaneous person.

Yes.

Examples:

• en spontan person = a spontaneous person
• en spontan idé = a spontaneous idea
• et spontant svar = a spontaneous answer

So the adjective can be used both:

• after er: Hun er spontan
• before a noun: en spontan person

Put ikke after the verb:

• Hun er ikke spontan. = She is not spontaneous.

That is the normal position in a simple sentence like this.

Swap the verb and the subject:

• Er hun spontan? = Is she spontaneous?

This is very common in Norwegian yes/no questions.

In this simple sentence, yes, it is very similar:

• Hun = subject
• er = verb
• spontan = adjective

So it matches English quite closely: She is spontaneous.

But Norwegian often follows the verb-second rule in main clauses, so the order can change if something else comes first:

• I dag er hun spontan. = Today she is spontaneous.

Here er still stays in the second position.

A simple English-friendly approximation is:

hoon ehr spon-TAHN

A few notes:

• hun has a vowel that is not exactly like English oo, but hoon is a decent approximation.
• er varies by dialect, but ehr is a useful approximation.
• spontan usually has the stress on the last syllable: spon-TAN.

If you want to sound more natural, listening to native audio is very helpful here.

Usually, yes.

It describes someone or something unplanned, natural, or acting on impulse:

• Hun er spontan. = She is spontaneous.
• Det var en spontan beslutning. = It was a spontaneous decision.

In everyday use, it is a normal and natural adjective in Norwegian.

Usually only the subject changes; er stays the same.

Examples:

• Han er spontan. = He is spontaneous.
• De er spontane. = They are spontaneous.

Notice that with de (they), the adjective becomes spontane in the plural.

So:

• singular person: spontan
• plural: spontane