It can be in some contexts. For example, "What is that?" "That is a dog." You would normally say "O köpek."
I'm going to remember this word by linking it to a song: "How much is that doggie in the window?" Answer: a kopek (like the Russian coin)
Oh, those demonic mnemonics! If you are a German teacher as implied you'll know that the Germans have a great expression for this: die "Eselsbrücke", translated literally, the donkey's bridge.