Questions & Answers about Huone oli täydellinen neliö.
Why are täydellinen and neliö in the nominative case here instead of the partitive?
In Finnish "A is B" sentences, when the subject you are describing (huone) is a single, countable thing, the noun following the verb olla (to be) goes in the basic nominative case. Because neliö is in the nominative, the adjective täydellinen must match it. You would generally only use the partitive after the verb olla if the subject was an uncountable mass noun (like water or coffee) or if the subject was plural.
In English, we use "square" for both shapes and town plazas. Can I use neliö for a town square too?
No, neliö only refers to the geometric shape. It is also commonly used in everyday speech as a short form for square meters (neliömetri) when talking about the size of an apartment. If you want to talk about a town square or market plaza, you should use the words tori or aukio.
How is the word täydellinen (perfect) formed?
It is built from the basic adjective täysi (full). The Finnish suffix -llinen is frequently added to words to create adjectives that mean "having the quality of" something. In this case, something that is entirely "full" or "complete" gives us the word for "perfect".