What are the symbols • and · respectively?

The symbols • and · are distinct typographic characters with overlapping historical functions but divergent modern applications, primarily in technical writing, mathematics, and digital communication. The filled circle, •, formally known as a bullet, is a typographic mark used chiefly for creating itemized lists, denoting key points, or serving as a visual separator in text. In contrast, the middle dot, ·, formally known as an interpunct, is a punctuation mark with a more specialized role, often indicating multiplication in mathematics (as an alternative to the × symbol), serving as a decimal point in some European contexts, or functioning as a separator in linguistic transcriptions and certain compound terms, such as in "A·B" for a chemical compound or "Xi·Jinping" in some romanization systems. Their visual similarity belies a fundamental difference in purpose: the bullet is a presentational glyph for organization, while the interpunct is an operational symbol within logical or notational systems.

The functional divergence stems from their origins and encoding standards. The bullet has its roots in early printing as a decorative element to highlight text, and in the digital age, it is encoded in Unicode as U+2022 BULLET. Its usage is largely stylistic and structural. The interpunct, encoded as U+00B7 MIDDLE DOT, has a longer history, tracing back to ancient Greek as a punctuation mark to separate words (the *stigmē teleia*). This historical role as a separator evolved into its modern technical applications. In computing and mathematics, the middle dot is explicitly defined as an operator; for instance, in scalar multiplication (k·v) or in denoting the dot product in vector algebra, though the latter more commonly uses a period or a dedicated dot operator. This technical specificity means the symbols are not interchangeable in formal writing, as substituting a bullet for a multiplication dot would be considered an error, akin to using a decorative dingbat in place of a mathematical operator.

In practical application, confusion frequently arises in word processors and web content, where automated list formatting often uses the bullet character, while the middle dot must be deliberately inserted via special character menus or specific keyboard shortcuts. The implications of misuse are context-dependent. In a business presentation or a web article, using a bullet where a style guide calls for a middle dot is a minor typographic issue. However, in academic, scientific, or technical documentation, such a substitution introduces ambiguity and can compromise clarity, potentially leading to misinterpretation of an equation or a formal notation. Therefore, the critical distinction lies not in their appearance but in their semantic load: the bullet is a passive visual cue, whereas the interpunct is an active syntactic element within a formalized language, whether mathematical, linguistic, or computational. Understanding this distinction is essential for precise communication in any field that relies on unambiguous symbolic notation.