WORD FORMATION

[Jnɨɨñɨ]

Nouns can be derived from verbs by adding, for instance, the suffixes -o or -i to the root "muista" (to remember). From there we can thus get "muisti" and "muisto" (memory), which are both results of rememberring something (the thing remembered).

However, there are some other different endings which indicate "the act of doing something" rather than "the result of doing something".

-nta ~ -ntä (noun)
etsi/ä = look for; etsintä = search

-e (noun)
puhu/a speak; puhe = speech

-nti (noun)
myy/dä sell; myynti = sale

-nto ~ -ntö (noun)
asu/a live; asunto = residence

-uu (noun)
kaivat/a long for; kaipuu = longing

-us ~ -ys (noun)
puolusta/a defend puolustus = defence

But I don't get the differences between any of these endings and the other
All of them seem to indicate "the act of doing something":
Etsintä=The act of looking for something (Search)
Puhe=The act of speaking (Speech)
Myynti=The act of selling (Sale)
And so on. So isn't there any difference? Could one then do something like the following?:

Starting with "Etsiä"...
-ntä: Etsintä
-e: Etse
-nti: Etsinti
-ntö: Etsintö
-uu: Etsuu
-ys: Etsys

1. Would these words even exist?
2. Would they mean something?
3. Would they all mean the same?
If not, what would they mean then?

[Miumau]

This is a very fascinating topic! And also not an easy one.

First important point: the ending -minen is the general way of forming nouns from verbs with the simple meaning "the act of doing something". This works with all verbs.
E.g.: lukeminen (<lukea), puhuminen (<puhua), syöminen (<syödä), etc.

Second important point: All of the other endings are more specific. You can't apply all endings to any verb (it depends on the type of the root of the verb). Some endings produce more specific or abstract meanings than the general -minen ending.
There is no (simple and easy) rule to this. Some endings are more common than others. Some are rare and you cannot really form new nouns by applying them to verbs.

The Kotus grammar, again, has a good overview on this phenomenon (in Finnish only). This page: http://kaino.kotus.fi/visk/sisallys.php?p=222 tells which endings can in general be applied to which type of verbs. Also there are detailed explanations on each type of ending.

Nouns can be derived from verbs by adding, for instance, the suffixes -o or -i to the root "muista" (to remember). From there we can thus get "muisti" and "muisto" (memory), which are both results of rememberring something (the thing remembered).

Yes, they are both formed from 'muistaa' but 'muisti' and 'muisto' do not mean the same thing, although both would be translated as "memory" in English.
muisti = memory as in the general capacity to remember things, and also the place where individual memories are stored
muisto = an individual memory of something specific that happened

So, all the 'muistot' are stored in the 'muisti'

However, there are some other different endings which indicate "the act of doing something" rather than "the result of doing something".

-nta ~ -ntä (noun)
etsi/ä = look for; etsintä = search

-e (noun)
puhu/a speak; puhe = speech

-nti (noun)
myy/dä sell; myynti = sale

-nto ~ -ntö (noun)
asu/a live; asunto = residence

-uu (noun)
kaivat/a long for; kaipuu = longing

-us ~ -ys (noun)
puolusta/a defend puolustus = defence

But I don't get the differences between any of these endings and the other
All of them seem to indicate "the act of doing something":
Etsintä=The act of looking for something (Search)
Puhe=The act of speaking (Speech)
Myynti=The act of selling (Sale)
And so on.

Yes, all can mean the act of doing something, but they can also have other meanings.
For example 'puhe' can also mean 'a speech' (something that someone holds at a party etc), so the result of the speaking itself, just as in English in this case.

'Myynti' can also mean 'the sales', the result of selling, as well as the act of selling itself.
For example: 'Tietokoneiden myynti kasvoi viime vuonna'. = Sales of computers increased last year. 'Tietokoneiden myynti on rankkaa työtä'. = Selling computers is hard work.

The ending -nto is a bit specific. 'Asunto' does not mean the act of living somewhere, but rather "residence" or "apartment". So it is a noun that has gotten a specific meaning. Practically all nouns with the -nto ending are like this: with a specific (abstract or concrete) meaning, that does not mean the act of doing itself.

So, in short... each of the endings listed above can be used to form nouns from verbs, but they attach to different types of verbs and have no definite meanings. They are just endings without any specific meanings in themselves.

So isn't there any difference? Could one then do something like the following?:
Starting with "Etsiä"...
-ntä: Etsintä
-e: Etse
-nti: Etsinti
-ntö: Etsintö
-uu: Etsuu
-ys: Etsys

1. Would these words even exist?
2. Would they mean something?
3. Would they all mean the same?
If not, what would they mean then?

1. No, except etsintä
2. The only one that means anything (can be applied to the verb etsiä) is etsintä. It actually means the same as etsiminen, just sounds a bit more abstract (this seems to be often the case when the -ntA ending can be applied to a verb). A bit like 'searching' ~ 'a search'.

In some cases, many different endings can be applied to the same verb, and they may or may not mean the same thing. Often, the endings other than -minen give more abstract meanings. Also these endings do not always produce nouns that mean the act of doing something.

For example:
painaa (to press; to push; to print) gives:
> painaminen = (the act of) pressing
> painanta = (the act of) pressing, but more specific; usually means 'printing', as in printing books
> paine = pressure
> paino = weight
> paini = wrestling
... and so on