Learn Finnish: Pöytä on viisi metriä leveä. - The table is five meters wide.

In Finnish, any basic number greater than one requires the noun immediately following it to be in the partitive singular. Because we are using viisi (five), the word metri must become metriä.

Since metriä is in the partitive, why isn't the adjective leveä in the partitive too?

The adjective leveä describes the subject of the sentence, pöytä (table), not the meters. Because pöytä is a single, countable whole object in the nominative case, the describing adjective must also be in the nominative case. It doesn't become partitive just because it sits next to metriä.

Is the word order for measurements always exactly like this?

Yes, when expressing the dimension of an object using an adjective, Finnish maps perfectly to English word order: [Number] + [Unit in partitive] + [Adjective of dimension]. "Five meters wide" translates directly to viisi metriä leveä.

How would this sentence change if we were talking about multiple tables?

It would become Pöydät ovat viisi metriä leveitä. The subject (pöydät) and the verb (ovat) become plural. The adjective (leveitä) becomes plural partitive to match the plural subject. Notice that the measurement itself (viisi metriä) stays exactly the same!