When to translate "ein" to describe people?

Answer 1

Hallo!

Generally, "ein/e" is not used before a noun when describing what people do, in a general sense, or the position they hold professionally.

For example:

Du bist Student/Studentin.

Er ist Lehrer.

Sie ist Informatikerin.

However, as soon as you qualify the noun in any way - either through an adjective or by any other means, the word "ein/e" is needed:

Du bist ein guter Student/eine gute Studentin.

The noun, "Student/Studentin", is qualified by an adjective, in this case by the adjective "gut" (with appropriate, grammatical endings, respectively).

Er ist ein talentierter Lehrer. (The noun, "Lehrer", is again qualified by an adjective, in this case "talentiert" (with the appropriate, grammatical ending).

Sie ist eine Informatikerin, keine Lehrerin.*

This example is different from the first two. "Eine" is needed here, because the noun, "Informatikerin", is qualified not by an adjective, as in the other examples, but rather by additional, contrasting information - "keine Lehrerin".

*This statement ("Sie ist eine Informatikerin, keine Lehrerin") is a possible response to a question, such as, "Ist Maria nicht Lehrerin?"