Punctuation formerly used as a sentence or paragraph divider. It is still sometimes used in calligraphy. Spanish uses an inverted question mark at the beginning of a question and the normal question mark at the end, as well as an inverted exclamation mark at the beginning of an exclamation and the normal exclamation mark at the end. Armenian uses several punctuation marks of its own. The full stop is represented by a colon, and vice versa; the exclamation mark is represented by a diagonal similar to a tilde , while the question mark resembles an unclosed circle placed after the last
Comma category by Lawvere, which involved the comma punctuation mark. Although standard notation has changed, since the use of a comma as an operator is potentially confusing, and even Lawvere dislikes the uninformative term "comma category" (Lawvere, 1963 p. 13), the name persists. The most general comma category construction involves two functors with the same codomain. Often one of these will have domain 1 (the one-object one-morphism category). Some accounts of category theory consider only these special cases, but the term comma category is actually much more general. Suppose that formula_1, formula_2, and formula_3 are categories, and formula_4 and formula_5 (for source