Learn Hardcore Finnish: Lähetän uutiskirjeen siskolleni sähköpostitse. - I send the newsletter to my sister by email.

Finnish normally omits personal subject pronouns because the verb ending already shows the person. Lähetän means I send / I am sending, so minä is usually unnecessary. You can add minä for emphasis or contrast (e.g., Minä lähetän… = I (not someone else) am sending…).

What tense is lähetän, and does it mean “I send” or “I am sending”?

Lähetän is the present tense (1st person singular) of lähettää (to send). Finnish present tense commonly covers:

habitual: I send
ongoing: I am sending
near future (often with context): I will send
So the exact English choice depends on context, even though the Finnish form stays the same.

Why is uutiskirjeen in the -n form, and what case is it?

Uutiskirjeen is the object in the so-called total object form. For many singular nouns, the total object looks like the genitive singular ending -n.
Here it typically implies a complete, bounded action: you are sending the newsletter (as a whole).

How would the meaning change if the object were uutiskirjettä instead?

Uutiskirjettä is the partitive object. It often suggests an incomplete/ongoing action or an unbounded quantity. For example, it could imply something like:

you’re in the process of sending it (not presented as “completed”)
you’re sending newsletters in general / some amount (depending on context)
With a single concrete newsletter, uutiskirjeen is the more typical “complete” choice.

What does siskolleni mean grammatically, and why that ending?

Siskolleni breaks down as:

sisko = sister
-lle = allative case (“to” / “onto”, used for recipients)
-ni = possessive suffix my
So siskolleni literally means to my sister.

Why use -ni (“my”) instead of saying minun siskolle?

Finnish often expresses possession with a possessive suffix. These are both possible:

siskolleni = to my sister (common, compact)
minun siskolle(ni) = also possible; adding minun emphasizes my
Often, if you use minun, you still keep the suffix (minun siskolleni), though in casual speech people may sometimes drop it.

What is sähköpostitse, and what case/form is it?

Sähköpostitse means by email / via email. The ending -itse forms an adverb meaning “by means of / via” (similar to postitse = by mail). It’s not a regular everyday “case” like inessive/allative; it’s a fossilized adverb-forming pattern used specifically for “by way of X.”

Could I also say sähköpostilla instead of sähköpostitse?

Often, yes, depending on what you mean:

sähköpostitse = via email (channel/method)
sähköpostilla = literally “with email”; can work colloquially for “by email,” but can feel less precise or may suggest “using email (as a tool)”
For “sent via email,” sähköpostitse is very idiomatic.

Is the word order fixed here? Can I rearrange it?

Finnish word order is fairly flexible, and changing it typically changes emphasis rather than basic meaning. For example:

Lähetän uutiskirjeen siskolleni sähköpostitse. (neutral)
Lähetän siskolleni uutiskirjeen sähköpostitse. (slightly more focus on the recipient early)
Sähköpostitse lähetän uutiskirjeen siskolleni. (emphasizes the method: by email)
The case endings keep the roles clear even when you move words.

How do I know uutiskirjeen is the object and siskolleni is the recipient?

Mostly from endings:

uutiskirjeen (total object form, -n) = what is being sent
siskolleni (-lle, allative) = to whom it’s being sent
Finnish relies heavily on these endings instead of position to show grammatical roles.

Is uutiskirjeen definite (“the newsletter”) or indefinite (“a newsletter”)?

Finnish has no articles (a/the), so uutiskirjeen can be either depending on context. The object form here mainly signals “a complete newsletter,” not definiteness. Context (previous mention, shared knowledge, etc.) decides whether English should be a or the.