Learn Finnish: Pieni hoitola on toisessa kerroksessa. - The small salon is on the second floor.

It comes from the noun hoito (care or treatment), combined with the suffix -la, which turns a word into a location or place of business. So, a hoitola is literally a "place of care" - usually translated as a salon, spa, or clinic.

What is the root verb behind hoito and hoitola?

The root verb is hoitaa, which means to care for, treat, or manage. From this verb, we get the noun hoito (the care), and then the place hoitola (the salon or clinic).

Why does Finnish use the inessive case (-ssa, meaning "in") for kerroksessa when the English translation says "on the floor"?

Finnish envisions a building as a three-dimensional space rather than just flat surfaces. Because you are located inside that specific level of the building, you use the inessive -ssa (kerroksessa) rather than the adessive -lla (on).

How does the word toinen (second) become toisessa?

Words ending in -nen change their ending to -se- before adding most case endings. So, toinen drops the -nen, adds -se- to form the stem toise-, and finally takes the inessive ending -ssa so it matches the case of kerroksessa.