An MKV file is a Matroska file. The Matroska Multimedia Container is an open standard free container format, a file format that can hold an unlimited number of video, audio, picture or subtitle tracks in one file. Matroska is an English word derived from the Russian word Matryoshka, which means nesting doll (the common Russian cylindrical-shaped doll within a doll, also known as a babushka doll). This is a play on the container (media within a form of media/doll within a doll) aspect of the matryoshka as it is a container for visual and audio data. The loose transliteration may be confusing to Russian speakers, as the Russian word matroska actually refers to a sailor suit.