Learn Finnish: Opaste on jalustan vieressä. - The sign is next to the pedestal.

This follows the Theme-Rheme (known-to-new) principle. By placing Opaste (the Theme) first, the speaker shows that 'the sign' is already the topic of conversation. The new information (the Rheme) is its location, jalustan vieressä. This structure specifically answers the question 'Where is the sign?'.

How would the meaning change if we swapped the word order to Jalustan vieressä on opaste?

The information structure would flip. Jalustan vieressä would become the known background information (the Theme), and opaste would become the newly introduced subject (the Rheme). In English, we use a 'There is...' structure for this: 'There is a sign next to the pedestal,' which answers the question 'What is next to the pedestal?'.

As a quick refresher, why does this sentence use the genitive form jalustan?

Because vieressä (next to) is a postposition. The vast majority of Finnish postpositions require the noun they follow to be in the genitive case. You can think of it literally as 'at the pedestal's side'.

What is the difference between opaste and other words for 'sign' like kyltti?

Opaste comes from the verb opastaa (to guide or direct). It specifically refers to an informational or guiding sign, such as a museum label, an airport directional sign, or a trail marker. A kyltti, on the other hand, just refers to the physical signboard itself, regardless of its purpose.