Jeg føler sterkt at planen er viktig.

I feel strongly that the plan is important.

Breakdown of Jeg føler sterkt at planen er viktig.

• jeg: I
• være: to be
• viktig: important
• at: that
• planen: the plan
• føle: to feel
• sterkt: brightly

Questions & Answers about Jeg føler sterkt at planen er viktig.

Why is it sterkt and not sterk in this sentence?

In Jeg føler sterkt at planen er viktig, sterkt is an adverb, not an adjective.

• sterk = adjective form, used with nouns:
  
  • en sterk mann – a strong man
  • en sterk plan – a strong plan
• sterkt = adverb form, used to modify verbs, adjectives, or whole clauses:
  
  • Jeg føler sterkt – I feel strongly
  • Jeg tviler sterkt – I strongly doubt

Here, sterkt modifies the verb føler (feel), so you must use the adverb form sterkt.
Using sterk would sound ungrammatical to a native speaker in this context.

Can I move sterkt to another place in the sentence, like in English?

Norwegian word order is stricter than English. The natural, neutral position for sterkt here is right after the verb:

• Jeg føler sterkt at planen er viktig. ✔ (normal)

These versions are either unnatural or wrong:

• Jeg sterkt føler at planen er viktig. ✖ (sounds very odd)
• Jeg føler at planen er sterkt viktig. ✖ (unusual and changes meaning; sterkt viktig would be “very important,” not “feel strongly”)
• Jeg føler at planen er viktig sterkt. ✖ (ungrammatical)

So in this sentence, keep sterkt right after føler.

What is the function of at in at planen er viktig, and can I leave it out like “I feel (that) the plan is important”?

at is a subjunction (a subordinating conjunction). It introduces a subordinate clause:

• at planen er viktig = that the plan is important

The structure is:

• Jeg (subject)
• føler sterkt (verb + adverb)
• at planen er viktig (object clause introduced by at)

Unlike English, spoken Norwegian almost always needs at here. Omitting it sounds wrong or at best very marked:

• Jeg føler sterkt planen er viktig. ✖ (ungrammatical in standard Norwegian)

So: keep at when you mean English “that” in sentences like this.

What is the difference between Jeg føler, Jeg synes, Jeg tror, and Jeg mener? Which is most natural here?

All four can translate as “I think” or “I feel” in English, but they’re used differently:

• Jeg føler (sterkt)

  • Literally “I feel (strongly)”.
  • Emphasizes emotion or intuition.
  • More about gut feeling, personal conviction.
  • Your sentence: Jeg føler sterkt at planen er viktig. = I feel strongly that the plan is important.

• Jeg synes at planen er viktig.

  • Neutral, everyday “I think / in my opinion”.
  • Very common in spoken language.
  • Slightly more about subjective opinion than deep emotion.

• Jeg tror at planen er viktig.

  • “I think / I believe” based on belief or assumption, not necessarily emotion.
  • Often used when you’re not 100% sure, or when guessing.
  • More like: I believe the plan is important (I think so, but I might be wrong).

• Jeg mener at planen er viktig.

  • “I think / I am of the opinion that…” with a more formal, argumentative tone.
  • Used in debates, discussions, when stating a considered opinion.

For everyday speech, Jeg synes at planen er viktig is probably the most natural way to say “I think the plan is important.”
Your original sentence with føler sterkt is stronger and more emotional: you really emphasize your conviction.

Why is it planen and not just plan? What is the difference?

Norwegian marks definiteness with endings, not just separate articles.

• en plan = a plan (indefinite)
• planen = the plan (definite)

So:

• Jeg føler sterkt at planen er viktig.
  = I feel strongly that the plan is important (a specific plan both speaker and listener know about).

If you said:

• Jeg føler sterkt at en plan er viktig.
  = I feel strongly that a plan is important. (any plan in general; sounds odd here without more context)

In most realistic contexts, you mean a particular plan that has already been mentioned, so planen is correct and natural.

Could I say Jeg føler virkelig at planen er viktig instead of Jeg føler sterkt?

Yes. Both are grammatically correct, but they have slightly different nuances:

• Jeg føler sterkt at planen er viktig.

  • Literally: I feel strongly that the plan is important.
  • Slightly more formal or literary.
  • Emphasizes the strength of your conviction.

• Jeg føler virkelig at planen er viktig.

  • Literally: I really feel that the plan is important.
  • Very common and natural in speech.
  • Sounds a bit softer and more conversational.

In everyday Norwegian, virkelig is often more idiomatic than sterkt in this position:

• Jeg synes virkelig at planen er viktig. – Very natural in spoken language.

Is at planen er viktig the subject or the object of føler?

In Jeg føler sterkt at planen er viktig:

• Jeg = subject
• føler = main verb
• sterkt = adverb modifying the verb
• at planen er viktig = object clause (what you feel strongly)

So the whole clause at planen er viktig is the object of føler.
Inside that clause, planen is the subject and er viktig is the predicate.

Why is it er viktig (present tense) and not some special form?

The embedded clause planen er viktig is just a normal present-tense sentence:

• planen = subject
• er = present tense of å være (to be)
• viktig = predicate adjective (“important”)

Norwegian uses the present tense much like English when stating opinions or general truths:

• Jeg føler sterkt at planen er viktig.
  
  • I feel strongly that the plan is important.

If you were talking about the past, you’d change the tense:

• Jeg følte sterkt at planen var viktig. – I felt strongly that the plan was important.

Can I say Jeg føler sterkt på at planen er viktig? I’ve seen føle på somewhere.

No, not in this meaning.

• Jeg føler sterkt på at … ✖ is not idiomatic for “I feel strongly that…”.

Norwegian føle på is used in more concrete or different senses:

• Jeg føler på stoffet. – I feel (touch) the fabric.
• Jeg føler på meg at noe er galt. – I have a feeling that something is wrong. (here på meg belongs with føler as an expression)

For your sentence, use føler without på:

• Jeg føler sterkt at planen er viktig. ✔
• Or more colloquially: Jeg føler virkelig at planen er viktig. ✔

Is Jeg føler sterkt at planen er viktig something people actually say, or does it sound too formal?

It is correct and understandable, but it leans a bit formal or written. In everyday spoken Norwegian, people might more often say:

• Jeg synes planen er veldig viktig.
• Jeg synes virkelig at planen er viktig.
• Jeg mener at planen er viktig. (in a discussion/debate)

Your sentence works well in:

• written arguments (emails, reports, essays),
• speeches,
• formal or serious discussions where you want to stress the strength of your conviction.

So it’s usable, but for casual conversation, synes/virkelig/veldig are more typical choices.