# Quotation marks When converting straight single quotes into curled single quotes, the application offers a variety of entities to use for encoding: * **regular** -- Do not encode. * **modifier** -- Encode as \ʼ, the modifier letter apostrophe. * **apos** -- Encode as \', curled when typeset to PDF. * **aposhex** -- Encode as \', the apostrophe's numeric value. * **quote** -- Encode as \’, the right single quotation mark, which is typically curled in HTML and XHTML documents by default. * **quotehex** -- Encode \’, the right single quotation mark's numeric value. When typsetting into a PDF document, only the semantically correct value of \' will be curled automatically. # History Quotation marks trace back to Ancient Greek, later adopted to the diplé (⸖) circa 625 BCE, foreshadowing its later curve. By the seventeenth century, quotation marks grew common. During the nineteenth century, Western Europe turned the convexity of quotation mark pairs outward. Early mechanical typewriters, circa 1825, lacked many punctuation marks. As technology improved, additional keys were added while some keys played dual roles (such as I for 1). Straight single and double quotes could be co-opted for quotation marks and apostrophes, feet and inches marks, and primes and double-primes. There wasn't a pressing need to type curled versions because humans excel at understanding from context. Eventually straight quotes were codified for computers. Unfortunately, the apostrophe carried with it the baggage from typewriters. That is, burgeoning encoding standards failed to let users capture the nuances of the English language; computers forced users to treat the apostrophe as a straight quote. Standards bodies suggested using the right single quotation mark for an apostrophe instead, shirking off its semantic meaning. Consequently, text containing English quotations, especially British English, is now riddled with ambiguity. Consider the sentence: > Ambiguity lurks in "'cause the horses'". Does `'cause` mean _because_ or _induce_? The answer determines whether an open left single quote is used or an apostrophe, semantically speaking. It's amazing how ancient decisions still affect modern systems.