Finnish has some words that will get the ending you add to them twice: once at the end of the word, and once in the middle. For example, mustamakkara “black sausage” will become mustaamakkaraa in the partitive, and mustassamakkarassa in the inessive case.

Unfortunately there isn’t a clear rule for when you will inflect both parts of the compound word and when you will only add the ending to the very end of the word. In addition, you can find contradicting information in different dictionaries and grammar explanations. This is mainly due to the fact that Finnish is moving away from the system where both parts can get the ending. Not all prescriptive grammars move along with the times at the same pace, so some sources will contain older information. For this article, I’m using Kielitoimiston sanakirja as the base for the inflection. This is just one source, but I find it a reliable one.

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1. [Adjective + Noun] vs. Compound Nouns
   1. Pitkä perjantai vs. pitkäperjantai
   2. Nuoripari and nuorimies
   3. Uusi kuu vs. uusikuu
   4. Vanha kaupunki vs. vanhakaupunki
2. Single vs. Double Inflection
3. Always Double Inflection
   1. Pronunciation
   2. Examples of always double inflection
   3. Place names and other proper nouns
   4. Place names with single inflection
4. Both Single and Double Inflection
   
   1. Word list
   2. Isosisko and isoveli vs. isoäiti and isoisä
   3. Mustamakkara
5. Always Single Inflection
6. Oma-
7. Double Inflection in Numbers
8. Example Sentences
9. Coming Soon(ish)

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1. [Adjective + Noun] vs. Compound Nouns

All the words on this page are compound nouns which have an adjective as their first part (e.g. pitkäperjantai, nuoripari, uusivuosi). Writing these words as a compound rather than as two separate words conveys that the meaning is different that the sum of the parts.

1.1. Pitkä perjantai vs. pitkäperjantai 

For example, the words “pitkä perjantai” (a/the long friday) don’t mean the same as the compound word pitkäperjantai (Good Friday). The former describes what kind of a Friday we are having, while the latter refers to the Christian celebration.

1.2. Nuoripari and nuorimies

The phrase nuori pari means “young couple”, while nuoripari often has the specific meaning of the young couple being married rather than just dating. Likewise, nuori mies means “a young man”, while the compound word nuorimies refers to a youngster, someone who is young and a male. Think of this last one as the difference between “a gentle man” and “a gentleman”.

1.3. Uusi kuu vs. uusikuu

When uusikuu is written as one word, we’re referring to the phase of the moon: “new moon” or “waxing moon”; in contrast with the “full moon”. When you write uusi kuu as two words, we’re not referring to the moon phase as part of the waxing and waning.

1.4. Vanha kaupunki vs. vanhakaupunki

The combination of the words vanha and kaupunki is interesting. When we use two words, vanha kaupunki means “a/the old city”, e.g. Turku on vanha kaupunki. When we write it as one word, with a capital letter: Vanhakaupunki, we mean the name of a specific part of Helsinki which is called Vanhakaupunki, e.g. Vanhakaupunki on kaunis alue Helsingissä. Thirdly, if we write it as one word, but without the capital letter, vanhakaupunki means “the old town, historic center”, e.g. Tallinnan vanhakaupunki on kaunis.

2. Single vs. Double Inflection

Even when spoken, pitkäperjantai is clearly different from “pitkä perjantai”. This is due to the fact that the compound noun will only be inflected at the end (pitkäperjantaina “on Good Friday”), while the word pair will have both words inflect (pitkänä perjantaina “on a long Friday”). There is a group of nouns, however, that will be written as one word, but still get inflected both in the middle and at the end of the word.

We can distinguish three groups:

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• Words that only get double inflection (e.g. uutenavuotena “at New Year’s”)
• Words that only get single inflection (e.g. kylmälaukussa “in the cooler”)
• Words that can get both single and double inflection (e.g. isovarpaan / isonvarpaan “of the big toe”

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Below, you can find examples of all three of these groups. I’ve inflected all the words in the genitive case. The same will be true, however, for all the cases.

3. Always Double Inflection

3.1. Pronunciation

So how can you tell whether you should write nuorimies or nuori mies? If the context doesn’t tell, this is very hard. In theory, a slight difference in pronunciation should upon close inspection be detectable between nuorella miehellä and nuorellamiehellä.

In Finnish, the main stress of a word lays on its first syllable. In addition, there are secondary stresses. This means that, with two separate words, you should be able to detect a slightly heavier stress on the “miehellä” than in the compound noun. This is, however, very hard to detect, especially for language learners.

3.2. Examples of Always Double Inflection

The words in this list will always get double inflection. This means that – as a learner of Finnish – you can’t tell based on hearing these words whether they’re one word or two. The difference in meaning between the compound noun and two separate words can be pretty small, but usually there is a difference.

3.3. Place Names and Other Proper Nouns

Placenames (#1) like New-Zealand often get case endings twice. The names of certain animal or plant species (#2) often also get double inflection. These are generally straight loanwords.

These words are written as one word in a way to distinguish the proper noun from a simple phrase with an adjective. When we write Uusikaupunki we mean the Finnish city, while uusi kaupunki means “a/the new city”. Both will get double inflection: Asun uudessa kaupungissa. “I live in a new city” vs. Asun Uudessakaupungissa. “I live in Uusikaupunki”.

3.4. Place Names with Single Inflection

Not all placenames (#1) inflect double. You’ll just have to learn them when you actually need them. People’s last names (#2) generally don’t get double inflection.

4. Both Single and Double Inflection are Possible

For some words, both single and double inflection are possible.

4.1. Word List

4.2. Isosisko and Isoveli vs. Isoäiti and Isoisä

The family words isosisko “big sister”, isoveli “big brother”, isoäiti “grandmother” and isoisä “grandfather” are interesting. The first two can have both single and double inflection (e.g. isosiskolla and isollasiskolla). Over time it has become more common to only use single inflection. This is already the case with isoäiti, which can also be inflected once (e.g. isoäidillä).

It is likely that the tendency will keep moving forward towards having the case only the very end of the word, but for now, both options are correct for isoveli and isosisko.

4.3. Mustamakkara

Mustamakkara is a traditional Finnish blood sausage, which is generally eaten with lingonberry jam. It’s one of the compound words that can get either single or double inflection. It’s interesting to see how this works in the Wikipedia article about mustamakkara. Below, you can find how many times each version of the word was used in Wikipedia.

5. Always Single Inflection

When faced with a compound noun that starts with an adjective, a little bell should go off in your head to think about its inflection. However, the default rule is to only inflect words once. Below, you can find some very common examples of this.

6. Oma-

Many of the sources that I read through before writing this article mention compound nouns starting in oma- separately. I suppose I’ll do so too!

7. Double Inflection in Numbers

We can actually count the Finnish numbers as words that inflect two times as well!  After all, when we inflect 20 (kaksikymmentä) in the cases, we get kahdenkymmenen (genitive), kahdestakymmnenestä (mistä) and kahdeksikymmeneksi (translative). You can read more about the inflection of numbers here.

8. Example Sentences

Below, you can find examples of those words that get the case ending twice in the word.

9. Coming Soon(ish)

In addition to nouns with double inflection, there is also a group of other words that do this. I plan on making separate articles about those in the near future. Currently not included are:

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• Joku: jonkun, jotakuta, jollakulla
• Jompikumpi: jommankumman, jompaakumpaa, jommallakummalla

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Read More Elsewhere

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• Kielikello: Monimuotoiset yhdyssanat
  
• Kielikello: Omatunnon kysymys
  
• Kielitoimiston ohjepankki: Yhdyssana: alkuosassa adjektiivi (isosiskolle ja isollesiskolle)
• Kielitoimiston ohjepankki: Nimien taivutus: adjektiivialkuiset nimet (Isotaloa, Mustassameressä)
• VISK: Kongruenssin esiintymisympäristöjä
• J. Korpela: Isosisko : isosiskon ~ isonsiskon – taipuuko yhdyssanan alkuosa?

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