Learn Hardcore Norwegian: Denne perioden føles lang og vanskelig.

denne perioden = literally this the period → natural English: this period
den bilen = that the car → that car
de bøkene = those the books → those books

So the pattern is:

denne / den / det / de
- definite noun (-en, -a, -et, -ene)

That is why you say denne perioden, not denne periode. The indefinite form periode would be wrong here.

Why is it denne and not dette?

Denne and dette must match the gender of the noun:

denne = this (for masculine and feminine / common gender nouns)
dette = this (for neuter nouns)

The noun periode is common gender (usually listed with the article en in dictionaries: en periode). So you must use denne:

denne perioden (this period) ✅
dette perioden ❌
dette tidspunktet (this point in time – tidspunkt is neuter) ✅

What exactly is føles? Is it from å føle?

Yes.

å føle = to feel (transitive / with an object, or about yourself)
- Jeg føler smerte. = I feel pain.
- Jeg føler meg trist. = I feel sad.
å føles (the -s form) = to feel, seem (intransitive, no object)
- Det føles rart. = It feels strange.
- Denne perioden føles lang. = This period feels long.

Formally, føles is the middle/passive -s form of føle, but in modern Norwegian it’s usually thought of as its own intransitive verb: å føles. You typically use føles with adjectives to talk about how something subjectively feels.

What is the difference between føles and er in this sentence? Could I say Denne perioden er lang og vanskelig instead?

You can say both, but the nuance is different:

Denne perioden er lang og vanskelig.
- More objective-sounding statement of fact: the period actually is long and difficult (e.g., in a schedule, objectively many weeks).
Denne perioden føles lang og vanskelig.
- Emphasizes subjective experience: it feels long and difficult to you, regardless of the actual length.

In everyday speech, people often prefer føles here when they want to stress how draining or tough the time feels, not just how it is on paper.

Why are the adjectives lang and vanskelig in their basic form and not lange?

In this sentence, lang and vanskelig are predicative adjectives, coming after the verb (føles):

Denne perioden føles lang og vanskelig.

Rules for predicative adjectives:

Singular common gender (masculine/feminine) → use the base form:
- perioden er lang
- boka er vanskelig
Neuter singular → add -t:
- huset er langt
- spørsmålet er vanskelig (here vanskelig does not take -t; some adjectives are invariant in neuter)
Plural → add -e:
- periodene er lange og vanskelige

So perioden is singular, common gender → base forms lang and vanskelig are correct. Lange would be for plural: Disse periodene føles lange.

Why is it lang and not lenge? What is the difference?

Lang and lenge are related but have different grammatical roles:

lang = adjective (describes a noun)
- en lang periode = a long period
- perioden føles lang = the period feels long
lenge = adverb (describes how long something lasts)
- Det varer lenge. = It lasts a long time.
- Det føles lenge siden. = It feels like a long time ago.

In your sentence, you are describing the period (a noun), so you need the adjective: lang.
If there were no noun, just it, you might use lenge:

Det føles lenge. = It feels like a long time.

Why is it en periode / perioden and not ei periode / perioda? Is the noun masculine or feminine?

In Bokmål, many nouns that historically were feminine can be treated as either:

masculine: en periode / perioden
feminine: ei periode / perioda

But in practice, for periode, the masculine/common gender form is strongly preferred and what you will usually see:

en periode (indefinite)
perioden (definite)

The feminine forms ei periode / perioda are technically allowed but sound dialectal or old-fashioned to many speakers. For standard Bokmål as a learner, stick with:

en periode
denne perioden

Could I say Denne vanskelige perioden føles lang instead? How does that change the meaning?

Yes, that is absolutely correct, but the nuance shifts slightly.

Original:

Denne perioden føles lang og vanskelig.
- You are describing how the period feels: long and difficult.

Alternative:

Denne vanskelige perioden føles lang.
- Here, vanskelige is an attributive adjective (before the noun), so you are labelling the period as the difficult period, and then saying it feels long.

Grammatically:

Attributive (before noun, with definite form) → adjective takes -e:
- den vanskelige perioden (the difficult period)
Predicative (after er/føles) → base form:
- perioden er vanskelig
- perioden føles vanskelig

So both sentences are fine; you just change what you emphasize.

Why does vanskelig not change form to vanskeligt in neuter, the way lang can become langt?

Adjectives in Norwegian fall into different patterns. Many take -t in neuter singular, but not all.

lang → langt (neuter)
- et langt år
vanskelig often stays the same in neuter:
- et vanskelig spørsmål

So:

Common gender: en vanskelig periode
Neuter: et vanskelig spørsmål (not vanskeligt in modern Bokmål)

The -t neuter ending is common, but some adjectives (especially those already ending in -ig, -lig, -sk) for practical purposes keep the same form in neuter.

Where would I put an adverb like virkelig or veldig in this sentence?

Adverbs that modify adjectives normally come right before the adjective they describe. So you can do:

Denne perioden føles veldig lang og veldig vanskelig.
Denne perioden føles virkelig lang og vanskelig.

You can also put a single adverb in front of both adjectives:

Denne perioden føles veldig lang og vanskelig.

Putting veldig after the adjective would sound wrong:

*Denne perioden føles lang veldig. ❌

Can I use other nouns like tid or fase instead of periode? Do they sound different?

Yes, but each has a slightly different feel:

Denne perioden føles lang og vanskelig.
- Neutral, somewhat formal; can be used about school terms, phases of life, treatment periods, etc.
Denne tiden føles lang og vanskelig.
- A bit broader and more emotional: this time in my life / these days feel long and difficult.
Denne fasen føles lang og vanskelig.
- Stronger sense of a phase or stage (e.g., of a project, a relationship, a child’s development).

All three are grammatical; choose based on context and what nuance you want.

How do you pronounce føles, perioden, and vanskelig?

Approximate pronunciation (standard Eastern Norwegian):

føles → [FØH-les]
- ø like the u in burn (British), but with rounded lips.
- Stress on the first syllable: FØH-les.
perioden → [pe-ri-OH-den]
- The o in the stressed syllable is like o in more (but shorter).
- Stress on -o-: pe-ri-OH-den.
vanskelig → [VAN-ske-li]
- g at the end is usually silent.
- Stress on the first syllable: VAN-ske-li.

Full sentence roughly: DEN-ne pe-ri-OH-den FØH-les LANG og VAN-ske-li.