With or without indefinite article ??

Question

Why should I say "Je suis UN oncle" instead of "Je suis oncle"? I shall say "Il est président / prof / boulanger", always omitting the indefinite article. Is it different for family relations? Thanks in advance for any help.

Accepted Answer

Bonjour Alfred,
When talking about your profession with the verb 'être', there is no indefinite article in French.

Il est avocat = he is a lawyer
Elles sont peintres = they are painters

See link here: dont-use-indefinite-articles-with-professions
Attention: C'est + [indefinite article] + profession

C'est un boulanger = he is a baker
C'est une infirmière = she is a nurse

See link on the French indefinite article 
When talking about family realtions, you don't say "je suis oncle/tante/cousin etc" BUT "je suis un oncle / une tante...". As for "frère/soeur", you would only tend to use the indefinite article to say that you have a brother/sister: "j'ai un frère / une soeur".
I hope this is helpful.
Bonne journée !

Answer

What about 'étudiant'? Do we omit Un before 'étudiant' too?

Answer

Bonjour Manpreet,
The same applies as above with 'étudiant':

Il est étudiant = he is a student
Elles sont étudiantes = they are students

C'est un/une étudiant(e) = he/she is a student
Bonne journée !