Punctuation two styles differ mainly in the way in which they handle quotation marks, particularly in conjunction with other punctuation marks. In British English, punctuation such as periods and commas are placed outside the closing quotation mark; in American English, however, punctuation is placed inside the closing quotation mark. This rule varies for other punctuation marks; for example, American English follows the British English rule when it comes to semicolons, colons, question marks, and exclamation points. Other languages of Europe use much the same punctuation as English. The similarity is so strong that the few variations may confuse a native English
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