The positive degree
Meidän talomme on pieni.
Our house is small.
The positive degree in the nominative singular has no marker - you just use the same form as the one you find in the dictionary entry. This is pretty self-evident to a lot of learners because it works in the same way in a lot of other languages, too.
When you move on to compare things, there are things to consider.
The comparative degree
In English: nicer, cooler, more interesting...
It’s relatively straightforward when we have a word like iso, big (my favourite for examples because it’s so simple!).
So, the positive is iso. To put it in the comparative, we simply add the comparative marker,
-mpi → isompi
Hänen talonsa on isompi kuin meidän.
His/her house is bigger than ours.
tärkeä (this word has 3 syllables, bare this in mind for later)
Tämä on tärkeämpi puhelu.
This is a more important phone call.
However, not all the words are as simple as iso.
Take pieni, small.
Meidän talomme on pienempi kuin hänen.
Our house is smaller than his/hers.
Now you’re probably wondering how that i turned into an e. Well, it’s because I added the comparative marker -mpi to the stem of the word, which for pieni is piene-. Another reason why the stem is so important to understand in Finnish.
A couple of examples:
onnellinen, happy → stem: onnellise- → the comparative: onnellisempi
Minä olen onnellisempi kuin koskaan.
I’m happier than ever.
väsynyt, tired → stem: väsynee- → the comparative: väsyneempi
Olen väsyneempi kuin eilen.
I’m more tired than yesterday.
There are instances where you have to change the stem a little before putting it in the comparative. The following conditions must be filled:
The word has two syllables
The stem ends in a or ä.
2-syllable word: halpa, cheap → stem: halva- → change a to e → halve- → the comparative: halvempi
2-syllable word: kylmä, cold → stem: kylmä- → change ä to a → kylme- → the comparative: kylmempi
Exceptions that have a life of their own:
hyvä (good) - parempi (better) - paras (the best)
pitkä (long) - pitempi / pidempi (longer) - pisin (the longest)
One more thing. Don’t forget the 2-syllable rule (like I sometimes do!). You may have noticed that the stem for the word tärkeä is tärkeä. Yes, it ends in ä but don’t be fooled - the word has 3 syllables: tär-ke-ä. So keep the ä. Having said that, in spoken language, that ä often turns in to an e regardless.
Standard Finnish: Tämä on tärkeämpi puhelu.
Spoken Finnish: Tää on tärkeempi puhelu.
The same goes for a lot of adjectives that have a similar form:
vaa-le-a, light, fair
Standard Finnish: vaaleampi
Spoken Finnish: vaaleempi
kor-ke-a, tall (building, not person)
Standard Finnish: korkeampi
Spoken Finnish: korkeempi
Ps. To emphasize the comparative degree, i.e. to say much bigger etc. you can use the following words:
vielä isompi - even bigger (in French: encore plus grand)
paljon isompi - much bigger
vähän isompi - a little bit bigger
huomattavasti isompi - considerably bigger
The superlative degree
Remember, we’re still talking about the nominative.
The superlative marker that you add to the stem is -in (the equivalent of the -est / the most ---).
For the superlative, there are a few more rules when it comes to the stem:
o, ö, u and y remain as they are
helppo → stem: helpo- → superlative: helpoin
a, ä and e get deleted
halpa, cheap → stem: halva- → superlative: halvin
i and ii turn in to an e
kiltti, nice, well-behaved → stem: kilti- → superlative: kiltein
kaunis, beautiful → stem: kaunii- → superlative: kaunein
→ VV → V
(two of the same vowel turn in to just one)
hidas, slow → stem: hitaa- → superlative: hitain
hyvä, good - paras / (parhain)
pitkä, long - pisin
uusi, new - uusin
lyhyt, short- lyhyin / lyhin
The next step is to practise forming the degrees of comparison in the nominative singular, and as you move on to different cases and the plural, I recommend learning the cases little by little at the same time, if you haven’t already.