Hän keksi uuden laitteen.

Hän is the 3rd person singular personal pronoun, and it can mean either he or she. Finnish does not normally mark gender in this pronoun, so the sentence itself does not tell you whether the person is male or female.

A useful extra note: in everyday spoken Finnish, people often use se instead of hän for people, but hän is the standard written form.

Finnish has no articles, so there is no separate word for a, an, or the.

That means uuden laitteen can mean a new device or the new device, depending on context. In this sentence, the natural English translation is a new device.

Keksi is the simple past (often called the imperfect) of the verb keksiä.

So:

• keksiä = to invent, come up with, think of
• hän keksi = he/she invented, came up with, thought of

The present tense would be hän keksii.

No. Keksiä has a broader meaning than English invent.

Depending on context, it can mean:

• invent
• come up with
• think of
• figure out
• make up (for example, a story or excuse)

In Hän keksi uuden laitteen, the object uuden laitteen makes invented / came up with a new device the most natural meaning.

Because uusi laite is the basic dictionary form, but in this sentence the phrase is the object of the verb, so it has to be inflected.

With a finished, complete action like this, Finnish uses a total object. In a normal affirmative sentence like this one, a singular total object usually appears in the genitive-looking form:

• uusi laite = a new device / new device
• uuden laitteen = a new device (as the complete object of the action)

So the idea is: the person invented one whole new device.

This is a very common question.

In function, uuden laitteen is the direct object of the verb. In form, laitteen looks like the genitive singular.

Many learner materials talk about this as the accusative object, but in most singular nouns the object form looks exactly like the genitive. So you can think of it like this:

• its job is object
• its shape here is genitive-like

A special true accusative form survives clearly mainly in personal pronouns, such as minut, sinut, hänet.

Because adjectives in Finnish usually agree with the noun they describe in case and number.

Here, laite appears as laitteen, so the adjective must match it:

• uusi laite = new device
• uuden laitteen = of a new device / a new device as a total object form

Also, uusi is not inflected by simply adding -n to the end. Its stem changes:

• uusi
• uuden
• uutta
• uudessa

So uuden is the correct inflected form of uusi.

That is just how this noun type works in Finnish.

Laite belongs to a group of nouns whose stem changes in other cases. So you get forms like:

• laite = device
• laitteen = of the device / device as total object form
• laitetta = device (partitive)
• laitteet = devices

So the stem is not always just laite-. In many forms it becomes laitte- or laittee-. This is something learners usually memorize as part of the noun’s pattern.

Hän keksi uuden laitteen is the neutral, basic word order: subject + verb + object.

But Finnish word order is fairly flexible because the endings show what each word is doing. You can move things around for emphasis, for example:

• Uuden laitteen hän keksi. = It was a new device that he/she invented.
• Hän uuden laitteen keksi. = possible, but more marked or literary

So the original sentence is the most normal version, but not the only possible one.

The present tense is:

Hän keksii uuden laitteen.

That can mean something like:

• He/she invents a new device
• He/she is inventing a new device
• sometimes even He/she will invent a new device, depending on context

Finnish present tense often covers meanings that English separates into present and future.

A rough guide:

• Hän → the ä is somewhat like the vowel in cat, though not exactly the same
• keksi → KEK-si
• uuden → UU-den with a long uu
• laitteen → LAIT-teen with ai as a diphthong and a long ee

A few useful pronunciation points:

• Stress is usually on the first syllable of each Finnish word.
• Double vowels are long: uu, ee
• Finnish spelling is very regular, so pronunciation is usually predictable from the written form.