Savi on pehmeää.

• savi = the subject
• on = is, the 3rd person singular present of olla = to be
• pehmeää = the adjective soft used as a predicate after on

So the structure is:

subject + verb + predicate adjective

This is a very common Finnish sentence pattern.

Because savi is a material / mass noun: clay, like water, milk, gold, etc.

With this kind of subject, Finnish often uses the partitive singular for the predicate adjective:

• Savi on pehmeää.
• Maito on kylmää.
• Kulta on kallista.

So pehmeää is the partitive singular of pehmeä.

This is one of those places where Finnish works differently from English. In English, you just say is soft. In Finnish, the adjective form changes.

It is partitive singular.

Base form:

• pehmeä = soft

Partitive singular:

• pehmeää

Even though it is in the partitive, it is not an object here. It is a predicate complement after olla.

No.

The verb olla normally does not take a direct object in sentences like this. Here, pehmeää is describing the subject savi.

So:

• savi = what we are talking about
• pehmeää = what quality it has

In grammar terms, pehmeää is a predicative adjective or predicate complement, not an object.

Normally, for this meaning, no: Savi on pehmeää is the natural form.

That is because savi is treated as a substance or material, and with material nouns Finnish typically uses the partitive predicate adjective.

Compare:

• Tyyny on pehmeä. = The pillow is soft.
  
  • tyyny is a countable object, so the adjective is pehmeä
• Savi on pehmeää. = Clay is soft.
  
  • savi is a material, so the adjective is pehmeää

Finnish does not have articles like English a/an and the.

So savi can mean, depending on context:

• clay
• the clay
• sometimes some clay

The exact English wording depends on the situation, but Finnish usually leaves that unstated.

Usually it sounds like a statement about clay as a material or about some clay in context.

So it can work as:

• a general statement about clay
• a comment on some clay already being discussed

Finnish often leaves that distinction to context instead of marking it with articles.

Yes, but Savi on pehmeää is the normal, neutral order.

Finnish word order is more flexible than English, and changing it can shift emphasis. But for a basic statement, this is the most natural order:

subject + verb + complement

A learner should use this version unless there is a specific reason to emphasize something else.

You would say:

pehmeä savi

That is different from Savi on pehmeää.

Why?

Because in pehmeä savi, the adjective is directly attached to the noun, so it agrees with it in the usual attributive way.

Compare:

• pehmeä savi = soft clay
• Savi on pehmeää = Clay is soft

This is a very useful contrast:

• before the noun: pehmeä
• after olla with a material noun: pehmeää

A rough guide:

• savi ≈ SAH-vi
• on ≈ on
• pehmeää ≈ PEH-meh-aa

A few helpful pronunciation points:

• Finnish stress is usually on the first syllable
• every written vowel is pronounced
• double vowels are longer
• ää is a long vowel sound, not two separate English-style vowels

So pehmeää should be held a bit longer at the end than pehmeä.