Learn Hardcore Finnish: Ellei sade jatku koko päivää, menemme iltapäivällä puutarhaan. - Unless the rain continues all day, we will go to the garden in the afternoon.

Meaning: Practically the same in most contexts.
Style/register:
- ellei sounds a bit more formal / written, often seen in texts, instructions, news, etc.
- jos ei is completely neutral and very common in everyday speech.
Conjugation: In theory ellei can inflect:
- ellen (if I don’t), ellet (if you don’t), ellei (if s/he/it doesn’t), ellemme, ellette, elleivät.
  In real usage, ellei(t) is by far the most frequent.

In this sentence you could safely replace ellei with jos ei without changing the meaning:

Jos sade ei jatku koko päivää, menemme…

Why is it sade jatku and not sade jatkuu?

This is because of the Finnish negative construction.

Positive:

Sade jatkuu koko päivän. = The rain continues the whole day.

Negative:

Sade ei jatku koko päivää. = The rain does not continue the whole day.

In a negative sentence:

The verb “ei” carries the person/number (here 3rd person singular).
The main verb (jatkua) appears in the “connegative” form, a short form without the personal ending:
- Base verb: jatkua
- 3rd sg positive: jatkuu
- Connegative form used with ei: jatku

With ellei, the ei is already built in:

Ellei sade jatku koko päivää…
= If the rain does not continue all day…

So jatku is exactly what you get in any 3rd-person negative form:

Sade ei jatku. / Ellei sade jatku…

Why is there no word for “the” before sade?

Finnish has no articles at all — no equivalent of English “a/an” or “the”.

sade can mean “rain”, “a rain”, or “the rain” depending entirely on context.
In this sentence, context suggests “the rain” (the rain we are currently experiencing or expecting).

So Finnish:

Ellei sade jatku koko päivää…

English:

If *the rain doesn’t continue all day…*

What case is päivää in koko päivää, and why is that form used?

Päivää is the partitive singular of päivä (day).

päivä (nominative)
päivää (partitive singular)
päivän (genitive singular)

In koko päivää, it’s functioning as a duration expression:
→ for the whole day / all day long.

Finnish often uses the partitive for durations, especially when you’re talking about something that lasts for some (possibly continuous) amount of time:

Odotin sinua tuntikausia. – I waited for you for hours.
Satoi koko yötä. – It rained all night.

You will also see koko päivän (genitive) used with a very similar meaning, and many speakers would say:

Ellei sade jatku koko päivän…

Both koko päivää and koko päivän are understandable here; the key idea is that the noun is in an oblique case (not nominative) to express duration, not acting as a subject.

What does koko add to the meaning in koko päivää?

Koko means “whole / entire”.

päivä = day
koko päivä = the whole day / the entire day
koko päivää (here in partitive) = for the whole day / all day (long)

So koko emphasizes that we’re talking about the entire day, not just some part of it.

Why is there a comma before menemme?

Finnish uses a comma between a subordinate clause and the main clause.

Here:

Subordinate (conditional) clause: Ellei sade jatku koko päivää
Main clause: menemme iltapäivällä puutarhaan

When the subordinate clause comes first, a comma is obligatory:

Ellei sade jatku koko päivää, menemme iltapäivällä puutarhaan.

If you reverse the order, you usually still use a comma before the conditional clause:

Menemme iltapäivällä puutarhaan, ellei sade jatku koko päivää.

Why does menemme look like present tense if the meaning is “we will go”?

Finnish does not have a separate future tense. The present tense is used for:

Present time
Future time

Here, menemme is present tense of mennä (to go), 1st person plural:

me menemme = we go / we are going / we will go

The future sense comes from context:

A condition referring to the (near) future: Ellei sade jatku koko päivää…
An action that will happen after the condition is known: …menemme iltapäivällä puutarhaan.

So in translation, English needs “will go”, but Finnish just uses present.

Why is it iltapäivällä and not just iltapäivä?

Iltapäivällä is the adessive case of iltapäivä:

iltapäivä = afternoon (nominative)
iltapäivällä = in the afternoon / during the afternoon

The -lla/-llä (adessive) ending is commonly used with times of day to mean “at/in/during”:

aamulla – in the morning
päivällä – in the daytime
iltapäivällä – in the afternoon
illalla – in the evening
yöllä – at night

So menemme iltapäivällä = “we will go in the afternoon”.

What does the ending in puutarhaan mean, and how is it different from puutarhassa?

Puutarhaan is the illative form of puutarha (garden).

puutarha – garden (basic form)
puutarhassa – in the garden (inessive, internal location)
puutarhaan – to/into the garden (illative, movement into)

The illative ending here is -an with an extra h inserted:

puutarha → stem puutarha- → puutarhaan (to the garden)

Compare:

Olemme puutarhassa. – We are in the garden. (location)
Menemme puutarhaan. – We (will) go to the garden. (movement/direction)

In this sentence, we are going to the garden, so puutarhaan is the correct form.

Why is there no me before menemme?

In Finnish, personal endings on the verb already show the subject, so the pronoun is often omitted unless you want to emphasize it.

menemme = we go / we will go
(the -mme ending marks 1st person plural)
me menemme = also correct, but often more emphatic, like “we (as opposed to someone else) will go”.

So:

Ellei sade jatku koko päivää, menemme iltapäivällä puutarhaan.
is the most natural everyday form.
Ellei sade jatku koko päivää, me menemme iltapäivällä puutarhaan.
would subtly stress the “we”.

How would this sentence typically look in more colloquial everyday Finnish?

A very natural colloquial rephrasing would be:

Jos ei sada koko päivää, mennään iltapäivällä puutarhaan.

Changes compared to the original:

Ellei sade jatku → Jos ei sada
- Using jos ei instead of the more formal ellei.
- Using the verb sataa (to rain) instead of the noun sade:
  - ei sada = it doesn’t rain.
menemme → mennään
- mennään is the so‑called passive form, but in spoken Finnish it often means “let’s go / we go”.
- Very common in everyday speech for “we”.

The meaning is essentially the same:

If it doesn’t rain all day, we’ll go to the garden in the afternoon.