Learn Turkish: Yeni dekorasyon için ya mobilyaları ya da aydınlatmayı değiştirmemiz lazım. - For the new decoration, we need to change either the furniture or the lighting.

The core structure for 'either... or...' in Turkish is ya... ya.... Adding da to the second part to make it ya... ya da... is extremely common and sounds very natural. It doesn't change the meaning at all; it just adds a slight emphasis, similar to saying 'or else' in English.

Why do both mobilyaları and aydınlatmayı end with the accusative suffix -(y)ı?

They are both specific direct objects of the verb değiştirmek (to change). When you list multiple items using ya... ya da..., both items must take the grammatical case ending required by the verb. Since we are talking about specific things (the furniture and the lighting), both get the accusative ending.

How does değiştirmemiz lazım mean 'we need to change'?

To express needing to do an action, Turkish often uses a verbal noun (similar to an English '-ing' word) with a possessive ending, followed by the adjective lazım (necessary). Here, değiştirme means 'changing' and -miz is the possessive ending 'our'. So, değiştirmemiz lazım literally translates to 'our changing is necessary'.

Why doesn't yeni dekorasyon take any special endings before için?