When to put an i in the middle of (or after) a word in Finnish

Finnish has eight vowels, but i it is definitely the most popular one when it comes to functioning as a marker, being used for making new words or joining Finnish endings to foreign names. Please leave a comment if I forgot something.

1. Making loan words

Loan words are often among the first words that students learn, because they are so easy to remember! Just ad an i at the end of the word in another language, and it might be a real word in Finnish. Sometimes we also change or double the consonant. (With verbs, the ending is -ata. I'll write about that later.)

• posti - a post office, mail
• kahvi - coffee
• presidentti - a president 

Loan words can also end with other vowels, but i is the most common one. You can read more in my post about the loan words. 

2. A glue between a consonant and an ending when declinating names

If a name ends with a vowel, we just add the ending: 

• Hanna > Hannan kanssa - with Hanna

If a name ends with a consonant, we add an i and then the ending: 

• Max > Maxin kanssa - with Max
• Charles > Charlesin kanssa - with Charles
• Exception: Matias > Matiaksen kanssa - with Matias (also Topias, Markus and other names ending with as, us or os can behave like this.)

Notice that if a word ends with a consonant but is pronounced with a vowel, we add an apostrophe, heittomerkki, and then the ending:

• Louis Theroux > Louis Theroux'n kanssa - With Louis Theroux

3. Past tense marker

We put an i or si between the verb stem and a personal ending to express that something happened in the past. 

• sanon > sanoin  - I say > I said
• pelaan > pelasin - I play > I played

Sometimes vowels disappear or change, but there's always an i in the positive past tense.

• olen > olin - I am > I was
• maksan > maksoin - I pay > I paid

You can read more in my post called Past tense in a nutshell.

4. Plural marker

The nominative plural marker is t:

• talo > talot - a house > houses
• laukku > laukut - a bag > bags
• kissa > kissat - a cat > cats
• nainen > naiset - a woman > women

However, in all other cases, the marker is i. 

• laukussa > laukuissa - in a bag > in bags
• kadulla > kaduilla - on a street > on streets

When i is placed between two vowels, it becomes j. This happens sometimes with plural genitive and with plural partitive. 

• talo > taloja - a house > houses
• kissan kanssa > kissojen kanssa - with a cat > with cats

Sometimes the last vowel of the stem changes or disappears before the i: 

• Minä tykkään kissasta. > Minä tykkään kissoista. - I like a/the cat. I like cats. 
• Tykkään suomalaisesta oluesta ja suomalaisista. - I like Finnish beer and Finns.

Read all my posts about the plural forms: 

• T-plural or plural partitive?
• 100 words in plural partitive
• Long words in plural partitive
• Plural genitive
• Consonant change in nouns

I know. The plural is quite tricky, so I should write more about it. 

About the author of Random Finnish lesson: 

My name is Hanna Männikkölahti. I am a professional Finnish teacher who gives private online lessons and simplifies books into easy Finnish. Please read more in www.linktr.ee/hannamannikkolahti and follow this blog, if you want to be the first one to know when I post something new.