Year 342 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Ahala and Rutilus (or, less frequently, year 412 Ab urbe condita). The denomination 342 BC for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
The Greek philosopher, Aristotle, is invited by Philip II to his capital at Pella to tutor his son, Alexander. As the leading intellectual figure in Greece, Aristotle is commissioned to prepare Alexander for his future role as a military leader.
Philip begins a series of campaigns in Thrace with the aim of annexing it to be a province of Macedonia. When the Macedonian army approaches Thracian Chersonese (the Gallipoli Peninsula), an Athenian general named Diopeithes ravages this district of Thrace, thus inciting Philip's rage for operating too near one of his towns in the Chersonese. Philip demands his recall. In response, the Athenian Assembly is convened. Demosthenes convinces the Athenians not to recall Diopeithes.