Learn Hardcore Turkish: Yoğun sis yüzünden karayolu kapandı. - The highway was closed due to dense fog.

Turkish doesn’t use definite or indefinite articles. Nouns stand alone, and whether it’s “the road” or “a road” is inferred from context rather than a separate word.

What exactly does karayolu mean?

karayolu is a compound of kara (land) + yol (road), literally “land-road.” In practice it means “main road” or “highway.” For “motorway/freeway,” Turkish often uses otoyol.

Why is kapandı used instead of kapatıldı? Isn’t that passive?

kapanmak is an intransitive verb meaning “to close” or “to become closed.” So kapandı = “it closed” (no agent needed).
kapatmak is transitive (“to close something”), and its passive is kapatıldı (“it was closed [by someone]”). Since fog itself causes the closure, Turkish uses kapanmak, not the passive of kapatmak.

Why isn’t there a pronoun like “it” in kapandı? How do I know what closed?

In Turkish the subject pronoun is usually dropped because the verb ending tells you the person/number. The -dı in kapandı marks 3rd person singular (“he/she/it”). From context you understand “it” = karayolu.

What does yüzünden mean, and how do I attach it to sis?

yüzünden is a postposition meaning “because of.” It expresses cause and attaches to the noun:
• colloquially: sis yüzünden (“because of fog”)
• more formally: add the genitive -in → sisin yüzünden
Both are understood; dropping -in is very common in speech.

Could I use something else like sisten dolayı instead of sis yüzünden?

Yes. Alternatives:
• sisten dolayı (“due to fog”) – neutral form
• sisten ötürü – slightly more formal
• sisten kaynaklanan – “originating from fog” (more written style)
All convey the same basic idea; choice depends on formality and style.

What does yoğun mean, and why does it come before sis?

yoğun means “dense,” “thick,” or “heavy.” In Turkish adjectives always precede the noun they modify, so yoğun sis = “thick/heavy fog.” Turkish does not place adjectives after nouns (no post-nominal adjectives).

Why is the verb always at the end? What’s the word order here?

Turkish is generally SOV (Subject-Object-Verb). In this sentence:
1) Yoğun sis yüzünden = adverbial phrase (cause)
2) karayolu = subject
3) kapandı = verb (always at the end)

Why is karayolu singular here? Could I say karayolları kapandı?

It’s singular because you’re talking about a specific road/highway being closed. If multiple highways closed, you’d use the plural: karayolları kapandı (“highways closed”). Singular/plural reflects exactly how many roads you mean.