You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Letter_case

Context:
Letter case is often prescribed by the grammar of a language or by the conventions of a particular discipline. In orthography, the uppercase is primarily reserved for special purposes, such as the first letter of a sentence or of a proper noun, which makes the lowercase the more common variant in text. In mathematics, letter case may indicate the relationship between objects with uppercase letters often representing "superior" objects (e.g. X could be a set containing the generic member x). Engineering design drawings are typically labelled entirely in upper-case letters, which are easier to distinguish than lowercase, especially when space restrictions require that the lettering be small.

Question:
What is often prescribed by the grammar of a language or by conventions of a particular discipline?

Letter case