Pyöritä dreijaa hitaasti.

Pyörittää is the dictionary form, meaning to spin / to turn something.

Pyöritä is the 2nd person singular imperative, so it means spin! / turn! when giving a command to one person.

So the sentence uses the command form, not the infinitive. This verb also shows a stem change: pyörittää → pyöritä. That single t is normal here.

Dreijaa is the partitive singular of dreija.

So:

• dreija = basic form
• dreijaa = partitive singular

For many Finnish words ending in -a / -ä, the partitive singular is made by adding another vowel, so you get a long vowel:

• kirja → kirjaa
• dreija → dreijaa

Finnish often uses the partitive object when the action is seen as:

• ongoing
• incomplete
• not leading to a clear finished result

That fits pyöritä dreijaa very well. Spinning a wheel is an ongoing activity, not something you normally complete in the same way as, for example, eat the apple.

So dreijaa sounds natural because the command is basically telling someone to keep the wheel turning slowly, not to bring the action to a final endpoint.

It is a command to one person.

The form pyöritä is singular imperative.

If you wanted to command more than one person or use the plural/formal imperative, you would say:

Pyörittäkää dreijaa hitaasti.

In Finnish, commands usually do not include the subject pronoun.

So instead of saying something like You spin the wheel slowly, Finnish normally just says:

Pyöritä dreijaa hitaasti.

The verb form itself already shows that the command is directed at you (singular). Adding sinä would usually sound emphatic or marked.

Hitaasti is an adverb, and it tells you how the action is done.

It comes from the adjective hidas = slow.

So:

• hidas = slow
• hitaasti = slowly

This is a very common Finnish pattern: adjective-like base + -sti to make an adverb.

This sentence has a very natural, neutral order:

verb + object + adverb

• Pyöritä = verb
• dreijaa = object
• hitaasti = adverb

Finnish word order is fairly flexible, but changing the order usually changes the emphasis. The given order is the most straightforward way to say it.

This is a very useful pair:

• pyöriä = to spin / rotate oneself, without a direct object
• pyörittää = to spin / turn something, with a direct object

So:

• Dreija pyörii. = The wheel is spinning.
• Pyöritä dreijaa. = Spin the wheel.

In your sentence, pyörittää is needed because someone is making the wheel spin.

A few key points:

• Stress is on the first syllable of each word.
• y is like German ü or French u.
• ö is like German ö or French eu.
• aa is a long a sound, held a bit longer than a short a.

A rough guide:

• PYÖ-ri-tä
• DREI-jaa
• HI-taa-sti

Also, in dreijaa, the aa is long, so do not pronounce it like a short English a.