“Sind Sie Ingenieur?” should be “Sind Sie ein Ingenieur?”

Question

This question has also an answer in German:
Wann wird ein Beruf mit dem unbestimmten Artikel verwendet?

While studying for the A1 exam, I’ve stumbled upon the following sentence:

“Sind Sie Ingenieur?” – Are you an engineer?

And I can’t understand why there isn’t the “ein”/“eine” article.

Answer 1

This is a very subtle point of German grammar that native speakers don't necessarily get right. It is most often discussed in connection with John F. Kennedy's speech in Berlin.

1. Ich bin Berliner.
2. Ich bin ein Berliner.

1 is what I could say because I am living in Berlin. I might also say it if I lived elsewhere but had been born in Berlin, or had grown up in Berlin. Personally I wouldn't say 2 (yet), because I haven't been living in Berlin for long enough to feel a strong sense of identity with the city.

Kennedy wanted to express that he was a Berliner in the second sense, and therefore 2 is what the German who wrote his speech gave him to say in German. (Everybody understood this correctly. The recording dispells the myth that the crowd fell into laughter because outside Berlin ein Berliner can also refer to what Americans would call a jelly-filled donut. They only laughed later on, when Kennedy thanked his translator for 'translating' this German sentence to German.)

The distinctions in case of jobs and professions are similar:

1. Ich bin Ingenieur.
2. Ich bin ein Ingenieur.

1 is the normal way of saying this if you have an engineering degree or if you are working as an engineer. 2 expresses a special meaning such as having been born an engineer and behaving like one, whether you ever trained for or worked in the profession or not.

Answer 2

Ein Ingenieur would work as well, but in this case it's a generalized question, so this is fine without the article as well:

Compare

Are you American?

vs.

Are you an American?

Answer 3

English uses the indefinite article with indication of profession as in

• He is a teacher/ an engineer/ a journalist.

German does not use an article:

• Er ist Lehrer/ Ingenieur/ Journalist.

Answer 4

Like in english too, there are three types of articles:

definite articles:

Ich bin der Bauer.
I am the farmer.

You might use this article, when you are the only one farmer in a bigger group, and you are member of this group because you are a farmer. Someone is asking all participants: Who of us is the farmer? and then you might answer with the sentence above.

But you could also ask explicitly for the farmer:

Wer ist der Bauer?
Who is the farmer?

indefinite articles:

Ich bin ein Bauer.
I am a farmer.

This is when you are one of many farmers (and many other people), and when you are asked for your profession. Or you ask yourself a question:

Sind Sie ein Bauer?
Are you a farmer?

the null article:

Ich bin Bauer.
I am farmer.

The null-article is also suitable when you are asked for your profession. And here are the null-article-questions:

Sind Sie Bauer?
Are you farmer?

Since I am not an English native speaker (but a German native speaker) I am not sure, how widely use the null-article-version is in english.