The letter "S" has multiple meanings depending on context. In informal digital communication, "S" can represent a smile, often used to convey a positive emotional reaction.4 It is also used as a shorthand for sarcasm when written as "/s" at the end of a statement, signaling that the preceding text should be interpreted ironically.712 This usage originated as a way to clarify tone in text-based conversations where sarcasm might otherwise be misunderstood.510

In typography, "S" refers to the 19th letter of the English alphabet and has historical variants such as the long s (⟨ſ⟩), an archaic form used in English and German printing from the 8th to early 19th centuries, particularly in the middle of words.2 The long s was eventually replaced by the modern "round s" at word endings and in specific letter combinations.2

In technical contexts, "S" has specialized meanings: it denotes the possessive case in grammar (e.g., "man's"), represents the plural form of nouns (e.g., "boys"), and is used in abbreviations such as "S" for "second" in time measurement or "S" for "sacrifice" in baseball.9 In computing, "S" is the 19th column in spreadsheet programs like Excel 4 , a keyboard shortcut for tools in software such as Adobe Photoshop and Microsoft Paint 4 , and a character in regular expressions where "\s" matches whitespace.4

In legal and academic writing, the section sign (§) is used to reference specific sections of a document, often appearing as a double "S" symbol.6 Additionally, in some contexts, "/s" may denote a signature, particularly in formal or electronic documents, where it indicates a conformed or substituted signature.11

In mathematics and science, "S" can represent various concepts, including entropy in thermodynamics, strangeness in physics, serine in biochemistry, and sulfur in chemistry.9 It is also used in prescriptions to mean "let it be written" or "sign".9