Sputnik (Спутник, Russian for "satellite"[1]) is a name for multiple spacecraft launched under the Soviet space program. "Sputnik 1", "Sputnik 2" and "Sputnik 3" were the official Soviet names of those objects, and the remaining designations in the series ("Sputnik 4" and so on) were not official names but names applied in the West to objects whose original Soviet names may not have been known at the time.
^NOTE: The Russian word "sputnik" can have many meanings: "satellite", "travelling companion", "fellow traveller", etc. However, in astronomy, it means only "satellite".