"Your city is big, Samia."
Translation:مَدينَتِك كَبيرة يا سامْية.
Hanneke630996, if you have really heard samiyatun, it is grammatically incorrect. After vocative particle (Harf nida) yaa, the noun cannot receive tanween (e.g., -un). In this case, it should be "samiyatu" (ie. in Formal Standard). But, oftentimes people say, "yaa samia" informally.