Première rencontre en français pour débutants

Why is there no “un” in “je suis professeur”?

English needs an article for a job: “I am a doctor.” French drops it after être: je suis docteur, je suis professeur, elle est médecin. The same goes for devenir — il devient avocat. The article comes straight back the moment you switch to c’est (c’est un professeur) or add an adjective (je suis un bon professeur).

The rule holds for an unmodified job noun, which is why it survives so many everyday introductions. Which form to use for a woman is a separate and more recent question: professeure, autrice, ingénieure and cheffe have long been standard in Québec, and the Académie française accepted feminised job titles in 2019, so both the older masculine form and the feminised one are heard in France today.