In French, the indefinite articles un or une is not used when stating a profession.
When to omit the indefinite articles with professions in French
Look at these equivalent sentences:
In French we don't say un or une (a) when stating someone's profession.
We literally say "He is a lawyer", or "She is a doctor."
Also note: the job description changes if the person is feminine or masculine (see gender of professions)
In French, you always need an article in front of a group including an adjective, and that rule applies to professions:
See also Job titles differ in French depending on whether you're a man or a woman (nouns)
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