It is often confused with "tsarevich", which is a distinct word with a different meaning: Tsarevich was the title for any son of a tsar, including sons of non-Russian rulers accorded that title, e.g.
The title came to be used invariably in tandem with the formal style "Successor" (Naslednik), as in "His Imperial Highness the Successor Tsesarevich and Grand Duke".