Learn Hardcore Finnish: Ikkunasta näkyy vilkas katu. - You can see a busy street from the window.

Ikkunasta is in the elative case, formed by adding the suffix -sta to ikkuna (window). The elative expresses movement or viewpoint out of or from inside something. Here it gives the sense from the window, indicating the vantage point.

Why is the verb näkyy used instead of nähdä, and what does it mean?

Näkyä is an impersonal intransitive verb meaning to be visible. It describes that something appears or can be seen, rather than someone actively seeing it. With näkyä, the thing that is visible becomes the grammatical subject (in nominative), and the verb only has a third-person singular form: näkyy.

Why is katu in the nominative case and not another case?

With the impersonal verb näkyä, the visible object functions as the grammatical subject, so it stays in the nominative case. That is why katu remains in nominative singular, matching the verb’s third-person singular form näkyy.

What does vilkas mean, and how does it agree with katu?

Vilkas means busy or lively. Finnish adjectives agree with their nouns in case and number. Since katu is nominative singular, the adjective also appears in its nominative singular form: vilkas katu.

Why doesn’t Finnish use articles like the or a in this sentence?

Finnish has no definite or indefinite articles. Nouns simply stand alone in the appropriate case. Context tells you whether a noun is understood as the or a, so there’s no separate word for articles.

How would you say I see a busy street from the window in Finnish?

Use the transitive verb nähdä with an accusative object:
Ikkunasta näen vilkkaan kadun.
Here vilkkaan kadun is in the accusative singular as the object of nähdä, and minä (I) is omitted but implied by the verb form.

Can the word order be changed, and how does that affect meaning?

Yes. Finnish word order is fairly free because of case marking. For example:
Vilkas katu näkyy ikkunasta.
moves focus onto vilkas katu (the busy street). The neutral order Ikkunasta näkyy vilkas katu sets the viewpoint first. Changing order shifts emphasis but the basic meaning stays the same.