Tuossa on nainen.

Tuossa means something like there, right there, or in that spot. It points to a specific location, often something visible or being pointed at.

So Tuossa on nainen is essentially saying that a woman is located there.

Yes. Tuossa is a case form of tuo (that).

• tuo = that
• tuo + -ssa → tuossa

The ending -ssa is the inessive ending, which often means in. So very literally, tuossa is something like in that. In real usage, though, it often just works as a location word: there / right there.

On is the 3rd person singular form of olla, which means to be.

Here it translates as is, but in this kind of sentence Finnish often uses on where English uses there is:

• Tuossa on nainen. = There is a woman there.

Finnish does not need a separate dummy word like English there in there is.

Finnish has no articles, so there is no separate word for a, an, or the.

That means nainen can mean:

• a woman
• the woman

The context tells you which one is meant. In this sentence, it is naturally understood as a woman, because the sentence is introducing her.

Because this is a very common Finnish pattern for an existential sentence:

• [place] + on + [thing/person there]

So:

• Tuossa on nainen. = There is a woman there.

If you say:

• Nainen on tuossa.

that sounds more like The woman is there or The woman is in that spot. It shifts the focus to the woman, as if she is already known in the conversation.

Here nainen is in the nominative singular, which is the basic dictionary form.

In an existential sentence like this, a singular countable thing being introduced is often in the nominative:

• Tuossa on nainen. = There is a woman there.

So nothing special needs to be added to nainen here.

Because this sentence refers to one whole, countable person, so the nominative is natural.

The partitive is common in other situations, for example:

• with uncountable things: Tuossa on vettä. = There is water there.
• with indefinite plural: Tuossa on naisia. = There are women there.
• in negatives: Tuossa ei ole naista. = There is no woman there.

So nainen in nominative fits the idea of one woman being present there.

They are quite different.

• Tuossa on nainen. = There is a woman there.
• Tuo on nainen. = That is a woman.

So:

• tuossa = there / in that spot
• tuo = that

Just adding -ssa changes the meaning a lot.

All of them can be translated as there, but the nuance changes.

• tuossa = right there / in that spot, often specific and often visible
• tuolla = over there / at that place, often a bit broader or farther
• siellä = there, more general or neutral

In real speech, the borders are not always strict, but tuossa usually feels quite specific.

A rough guide:

• Tuossa ≈ TUO-ssa
• on ≈ on
• nainen ≈ NAI-nen

A few useful points:

• Stress is on the first syllable of each word.
• uo in tuossa is a diphthong.
• The ss in tuossa is pronounced longer than a single s.
• ai in nainen is also a diphthong.

So the rhythm is roughly:

TUO-ssa on NAI-nen

Yes. It is a normal and natural way to point out that someone is in a certain place.

It is especially natural when you are indicating a visible location, for example by looking or pointing:

• Tuossa on nainen. = There is a woman there.

It sounds like you are drawing someone’s attention to what is in that spot.