1. What is the Complement?

A complement is the part of a sentence that tells what (or what kind) the subject is (or isn’t). The complement can be either a noun or an adjective. The verb of the sentence is always “olla.” The subject of the sentence will appear in the basic form or the T-plural only, regardless of whether the subject is abstract or not.

2. What Case Should You Use?

The complement can appear in the following cases:

• The singular nominative: “Talo on punainen.”
• The singular partitive: “Viini on punaista.”
• The plural nominative: “Minun kengät ovat punaiset.”
• The plural partitive: “Mansikat ovat punaisia.”

The case you use can be both dependent on the type of subject you have in the sentence AND the type of complement you’re using. For example, “Tämä kuppi on valkoinen” will have valkoinen in the basic form because “kuppi” is a concrete subject. However, “Tämä kuppi on posliinia” will have posliini in the partitive because the complement is a material.

2.1. Singular Nominative Complements

2.1.1. With Concrete Subjects

If the subject of a sentence is a concrete thing and singular, the complement is in the singular nominative. Please note that even in a negative sentence you will be using the singular nominative rather than the partitive.

For example, a couch (sohva) is one concrete thing. That’s why we would say Sohva on uusi, pehmeä ja punainen, using the basic form of all three adjectives.

2.2. Singular Partitive Complements

2.2.1. With Abstract Subjects

When the subject is an abstract noun (something uncountable), the complement is in the singular partitive. Examples of abstract nouns are love, hate and friendship.

As such, we will say Sohva on ihana “the couch (a concrete thing) is wonderful”, but Rakkaus on ihanaa “love (an abstract thing) is wonderful”. In English, abstract subjects will usually appear in the sentence without an article: “The love is wonderful” doesn’t work.

Click if you want to take a more nuanced look at abstract nouns!

2.2.2. With Uncountable Foods

In addition to abstract nouns, I’ve also included “abstract” foods (e.g. kahvi, riisi, maito). These foods are “uncountable”; you can’t talk about “one rice” (you can talk about one GRAIN/PORTION of rice, but not count the rice itself). These words are mass nouns. These sentences can in English either have a definite pronoun the or appear without any pronoun.

The following isn’t a rule that always holds true, but it can help you in many situations: When trying to decide if something is countable or uncountable, it is often a good idea to ask yourself what happens if you cut the subject into pieces. Things that are uncountable can be divided into pieces without losing their identity.

For example, fabric can be cut into pieces, but the end result will still be fabric. In contrast, cutting a dress in pieces doesn’t leave you with a dress. As such, dresses are countable and fabric is uncountable. Similarly, cake is still cake when you cut it into pieces (it stays an uncountable amount of cake), but a piece of cake stops being a perfect slice and just turns into cake (an uncountable amount) when you do the same there.

2.2.3. With Subjects Expressing an Activity

When the subject expresses an activity, the complement will be partitive singular. Words expressing an activity are pretty often recognisable by the -minen at the end of them. Eg. uida is “to swim”, while uiminen and uinti are translated as “swimming”.

2.2.4. With Complements Expressing a Material

When the complement refers to the material or substance the subject is made of, you will use the partitive for the complement. In these cases it doesn’t matter whether the subject is countable. For example, “pusero” is definitely countable, but because we’re talking about the material, “silkki” will appear in the partitive case.

Compare: “Tämä pöytä on puuta.” vs. “Tämä pöytä on korkea.”

2.3. T-Plural Complements

The T-plural (aka plural nominative) is rarely used with complements, but it will be used with subjects that naturally only occur in the plural.

Your complement will get the -t ending when the subject is a word that expresses a single entity but (nearly) always appears in the plural. This is the case for:

1. Most celebrations
2. Things that can be perceived as containing two mirrored identical parts
3. Things that (almost) always come in pairs

2.4. Partitive Plural Complements

If the plural subject doesn’t mean one pair or entity (as in 2.3), the complement will be in the plural partitive. These sentences are marked as “regular” in the table below because the partitive plural is the default form for plural subjects. I have added some examples with the T-plural to allow you to compare sentence types.

3. Abstract Nouns

3.1. X on YZ – Love is a great feeling

A subject can be abstract or uncountable and still have a singular nominative complement. This is the case when there’s a noun in the complement (e.g. dessert, feeling).

3.2. X on Z – Love is a mystery

For the following sentences, the English translation can be a guideline when choosing the nominative over the partitive case. When you’re using an article (a, the) for the complement in English, you will use the basic form. This is in contrast with the sentences in section 3.3, where the English translation doesn’t have an article. The article tells us that these are countable nouns. While they are abstract, you can count them (e.g. two mysteries, three virtues).

3.3. X on Z:tä – Love is gratitude

You should compare these to the previous section 3.2. In the sentences below, you’re using a complement without an article in the English translation, so you’re using the partitive case for the complement. This is the case because these complements are abstract concepts rather than things you can count (e.g. there’s no such thing as “two gratitudes”).

3.4. X on V – Love is to give

Also note how a subject that is usually abstract can also be seen as a concrete thing when we’re talking about one of its kind. This is usually only the case with food.

That’s it for the complement! Do you have any questions?
Let me know in the comments below!

Related posts:

The Difference Between Mikä and Mitä The Finnish Object – Objekti Finnish Sentence Types Expressing Change: Tuloslause vs. Muutoslause Lausetyypit – Finnish Sentence Types