Learn Hardcore Finnish: Ajattelen sinua usein, kun kävelen puistossa. - I think of you often when I walk in the park.

Ajattelen is 1st person singular present indicative of ajatella (to think). The -n ending already means “I,” so minä is optional. Both Minä ajattelen… and Ajattelen… are correct; the latter is the neutral default.

Why is it sinua and not sinut?

Because ajatella takes a partitive object when you mean “think of/about” someone or something as an ongoing, non-resultative activity. So it’s Ajattelen sinua. The total/accusative form sinut is not used with ajatella in this meaning.

Should it be sinusta instead of sinua?

Use partitive sinua to mean “I think of you.” Use elative sinusta with ajatella when expressing an opinion about someone:

Ajattelen sinua. = I think of you.
Mitä ajattelet minusta? = What do you think of me?

What does usein modify here, and where else can it go?

Here usein modifies the main clause verb: you often think (in that situation). Word order is flexible:

Ajattelen sinua usein, kun…
Usein ajattelen sinua, kun… (emphasizes frequency) Be careful: Ajattelen sinua, kun kävelen usein puistossa means you walk in the park often; it doesn’t necessarily say the thinking is often.

Why is there a comma before kun?

Finnish separates subordinate clauses with a comma. When the main clause comes first, you put a comma before kun: …, kun …. If the kun-clause comes first, the comma goes after it: Kun kävelen puistossa, ajattelen sinua usein.

Does kun always mean “when”? Could it mean “because” here?

Here it’s temporal “when/while.” Kun can also mean “because” in many contexts, but if you want to be unambiguous for “because,” use koska.

Why kun and not milloin?

Kun introduces a temporal subordinate clause (“when”). Milloin is an interrogative (“when?”) used in questions or indirect questions:

Ajattelen sinua, kun kävelen puistossa.
En tiedä, milloin kävelen puistossa.

What tense/aspect is this? There’s no progressive in Finnish, right?

It’s present tense. Finnish present covers both English simple and progressive. With usein, it means a habitual action: “I often think of you when I’m walking in the park.”

What case is puistossa, and why not puistolla or puistoon?

Puistossa is inessive (-ssa/-ssä) = “in the park.” Related forms:

puistossa = in(side) the park
puistoon (illative) = into the park
puistosta (elative) = out of the park
puistolla (adessive) = at/on; used for certain places/events, but for a literal park as an area you are in, puistossa is standard.

Why kävelen and not something like olen kävelemässä?

Kun kävelen already means “when/while I’m walking.” The construction olla + -massa/-mässä (e.g., olen kävelemässä) emphasizes being in the middle of an activity; it’s not needed here.

Can I use a non-finite form instead of kun kävelen puistossa?

Yes: Ajattelen sinua usein kävellessäni puistossa. This uses the inessive of the second infinitive (kävellessä) with the possessive suffix -ni (“while I am walking”). It’s a bit more compact/formal.

Is ajattelen regular? Why not ajatelen?

Ajatella is a Type 3 verb (-ella/-ellä). Its present stem is ajattele-, so 1st person is ajattelen. Many -ella/-ellä verbs show this pattern:

ajatella → ajattelen
kävellä → kävelen
kuunnella → kuuntelen

Can I front elements for emphasis?

Yes, Finnish word order is flexible:

Sinua ajattelen usein, kun kävelen puistossa. (emphasizes “you”)
Usein ajattelen sinua, kun kävelen puistossa. (emphasizes frequency) Meaning stays, emphasis shifts.

How would this sound in casual spoken Finnish?

A natural colloquial version is: Mä ajattelen sua usein, ku kävelen puistossa. Notes:

mä/sä for minä/sinä
sua (colloquial partitive of sinä)
ku in place of kun in speech

How do I say this politely to one person, or to several people?

Polite/respectful singular: Ajattelen Teitä usein, kun kävelen puistossa.
Plural “you”: Ajattelen teitä usein, kun kävelen puistossa. Context clarifies whether teitä is polite singular or plural.

Could I drop usein or move the kun-clause to the front?

Yes. Variants include:

Ajattelen sinua, kun kävelen puistossa. (no frequency)
Kun kävelen puistossa, ajattelen sinua usein. (subordinate clause first; comma after it)