Learn Hardcore Finnish: Pidän puiston hiljaisuudesta iltaisin. - I like the park’s quietness in the evenings.

pitää + noun in -sta/-stä (elative) → to like / to be fond of
- Pidän kahvista. = I like coffee.
pitää kiinni (jostakin) → to hold on (to something)
pitää (jokin) + adjective → to keep something (in some state), e.g. Pidän oven auki. = I keep the door open.

In your sentence, the key is the -sta/-stä ending on hiljaisuudesta, which signals the “to like” meaning.

Why is it hiljaisuudesta (ending -sta) and not just hiljaisuus?

Because pitää (when it means to like) requires its object in the elative case (-sta/-stä):

Pidän + (mistä?) = “I like + (what?)”
hiljaisuus = quietness
hiljaisuudesta = (from/out of) quietness → used after pidän to express “I like quietness”

So grammatically it’s:

Pidän (mistä?) hiljaisuudesta.

Why does it say puiston hiljaisuudesta? What is puiston doing there?

puiston is genitive singular of puisto (park). The genitive here marks a relationship like English “the park’s”:

puisto → puiston = of the park / the park’s
puiston hiljaisuus = the park’s quietness
puiston hiljaisuudesta = (I like) the park’s quietness (with the required elative on the head noun)

So puiston modifies hiljaisuus.

Why is only hiljaisuudesta in the elative, but puiston is in the genitive?

Because the case required by the verb goes on the main noun of the noun phrase, not on every word in it.

Here the noun phrase is:

puiston (genitive modifier) + hiljaisuudesta (head noun in elative)

Think of it like English: you change quietness (the head) according to the grammar of the sentence, while park’s stays park’s.

What does iltaisin mean exactly, and what form is it?

iltaisin means in the evenings / in the evening time (habitually).

It’s a common Finnish adverb type meaning “at X times / on X occasions”:

ilta = evening
iltaisin = in the evenings (often implies “generally / usually in the evenings”)

It contrasts with:

illalla = in the evening (often a specific evening or “this evening” depending on context)
iltoina = on evenings (more literal plural adessive-like meaning, less common in this exact role)

Could I put iltaisin somewhere else in the sentence?

Yes. Finnish word order is flexible, and iltaisin can move for emphasis:

Pidän puiston hiljaisuudesta iltaisin. (neutral: “I like the park’s quietness in the evenings.”)
Iltaisin pidän puiston hiljaisuudesta. (emphasizes evenings: “In the evenings, I like…”)
Puiston hiljaisuudesta pidän iltaisin. (strong emphasis on the park’s quietness)

The core grammar stays the same.

What’s happening in hiljaisuudesta—where does the d come from?

The base noun is hiljaisuus (quietness). When you add endings, Finnish often inserts a consonant like d to make pronunciation smoother and to reflect historical stems.

A helpful way to see it:

hiljaisuus (dictionary form)
stem behaves like hiljaisuude- when inflected
hiljaisuude + sta → hiljaisuudesta

So the d is part of the inflected stem used before certain endings.

Is hiljaisuus related to hiljainen? How is the noun formed?

Yes:

hiljainen = quiet (adjective)
hiljaisuus = quietness (noun)

The ending -uus / -yys is a common way to form abstract nouns from adjectives, similar to English -ness:

hiljainen → hiljaisuus (“quiet” → “quietness”)

Could I also say Tykkään puiston hiljaisuudesta iltaisin?

Yes. tykätä works very similarly:

Tykkään puiston hiljaisuudesta iltaisin. = “I like the park’s quietness in the evenings.”

Both pitää and tykätä commonly take the elative:

Pidän (mistä?) …
Tykkään (mistä?) …

Nuance: tykätä can feel slightly more informal in many contexts, but both are very common.

Why isn’t the subject minä included? How do I know who likes it?

Finnish usually drops subject pronouns because the verb ending already shows the person:

Pidän = I like (1st person singular)

You can add minä if you want emphasis or contrast:

Minä pidän puiston hiljaisuudesta iltaisin. = “I like the park’s quietness in the evenings (maybe someone else doesn’t).”