To say what someone does for a living, French drops the article after être, devenir and rester: you say literally "I am engineer", never "I am an engineer". The article comes back only when you use c'est instead of il/elle est, or when the job is described by an adjective: c'est un bon ingénieur.
Examples
- Je suis ingénieur dans une entreprise de logiciels.
- I'm an engineer at a software company.
- Ma sœur est devenue avocate après cinq ans d'études.
- My sister became a lawyer after five years of study.
- Il est professeur, et c'est un professeur exceptionnel.
- He's a teacher, and he's an exceptional teacher.
- Avant, j'étais serveur, mais maintenant je suis étudiant en droit.
- Before, I was a waiter, but now I'm a law student.
The mistake to avoid
Learners copy English and say "Je suis un ingénieur", which sounds odd; use the article only after c'est or before an adjective + noun.
Where this fits in
Travail & études, French B1: Parler de son travail, de ses études et donner son opinion sur la vie professionnelle.