Finnish has five infinitives. This article focuses on the fourth infinitive, which is formed by adding -minen to the strong stem of verbs.

1. The Formation of the Fourth Infinitive

The fourth infinitive ends in -minen. You add this ending to the strong stem of the verb, which you can find by taking the third person plural form, and removing the -vat.

Some verbs also have a second noun describing the same action (eg. juokseminen = juoksu, uiminen = uinti). These forms have the exact same meaning. Not all verbs can have both versions, but every single verb can be made into a –minen noun.

2. The Inflection of the Fourth Infinitive

The -minen ending can make a noun out of a verb. The result can be called a “nounalized” (nominalized) verb . Since you change verbs into substantives, the result can be inflected into all the cases! To do that, you treat the -minen form as a noun with ending -nen (like for example punainen or suomalainen). For example:

3. The Use of the Fourth Infinitive

When using certain verbs in connection with other verbs, you sometimes have to turn them into a substantive. In English, you do this by adding -ing to the verb (e.g. I enjoy reading). In Finnish, you can recognise this specific form by the ending -minen. The –minen form of the verb is the “nounalized” verb!

3.1. Fourth Infinitive as a Subject

If you’d like to say “swimming is fun” or “cleaning is boring”, you will need the -minen form of the verb. These are all sentences with the verb olla, whose adjectives are always inflected in the partitive case. This is due to the complement rule (see 2.2.2) that says that subjects expressing an activity will have a partitive case complement.

3.2. Fourth Infinitive Rections

There are certain verbs that require the -minen form for any verbs attached to them. The most common ones are probably harrastaa and pitää. Of those two, harrastaa required the partitive form of the verb (harrastan lukemista) and pitää requires the -mistä form (pidän lukemisesta). You can read more about the verb harrastaa in our separate article.

In addition to harrastaa and pitää, there are quite a lot of verbs that require the inflected -minen form in sentences. Below are some examples, but you can find more of them in a separate article.

3.3. Fourth Infinitive Necessity

This section of the page deals with what is linguistically seen as the true fourth infinitive. It’s extremely rare. It expresses that an action is preferable (or in a negative sentence that the action is not preferable).

3.4. Puhui Puhumistaan

There is also a sentence construction that utilizes the fourth infinitive’s “nounalized” verb. With it, you can express a continual action. This construction consists of:

1. a verb describing the action, followed by
2. the “nounalized” version of the same verb. (the second part will be inflected into the partitive and be followed by a possessive suffix)