Monogatari (meaning story) is a common naming element of the Monogatari Series franchise for installments in the franchise. These installments are originally released as novels (containing 1 or more volumes) and are adapted into the anime adaptation through cours. They are contained within seasons and contain at least 1 arc within them.
While not always, many titles work as portmanteaus. The Bakemonogatari title for instance is made up of bakemono (化物) meaning monster or ghost and monogatari (物語) meaning legend or story. Ghostory acts as an effective English equivalent.
The Monogatari naming element shows up in other unrelated series titles such as Gokinjo Monogatari, Ore Monogatari, or Katanagatari.