Sign

A sign is an entity that indicates (represents) another entity to some agent (a human, animal or robot) for some purpose. It enters as a correlative in the relation of signification and significance (meaning for constructs) causing something else to come to the mind as its effects. According to the classic views of Aristotle, Augustine, and Aquinas, 'signification is a relationship between two sorts of things, which are signs and the kinds of things they signify'. To express a significance, the signs may both point out and stand for the entities signified, or just take the place and substitute as the symbols do. Also, signs or symbols may signify only mental constructs or they signify both constructs and external things. Then, since sings signify (express, denote, connote, or designate) but constructs mean, the significance of a sign in a language (natural or formal) equals the meaning of the mental construct designated by the sign.

The ontology of signs
Distinguishing natural and conventional signs, the traditional theory of signs set the threefold partition of things. Namely: 1. there are things that are merely things, functioning as the real world cause of meanings; 2. there are things that are also signs of other things (causally related natural signs of the physical world and mental signs of the mind); 3. there are things that are always signs, as languages (natural and artificial) and other cultural nonverbal symbols. Thus there are things which MAY act as signs without any respect to the human agent(the things of the external world, all sorts of indications, evidences, symptoms, and physical signals), there are signs wich are ALWAYS signs (the entities of the mind as ideas and images, thoughts and feelings, constructs and intentions); and there are signs that HAVE to get their signification (as linguistic entities and cultural symbols). So, while natural signs serve as the source of signification, the human mind is the agency through which signs signify naturally ocurring things, such as objects, states, qualities, quantities, events, processes, or relationships. Human language and discourse, communication, philosophy, science, logic, mathematics, poetry, theology, and religion are only some of fields of human study and activity where grasping the nature of signs and symbols and patterns of signification may have a decisive value.

Types of signs
The types and modes of signification vary according as the types of signs (or symbols), natural and conventional, vocal and nonvocal, material and cultural, and the kinds of things wich the signs (symbols) signify or stand for. Like the semantic relationships of words and ideas and things in the natural languages. In all, a sign can denote any of the following:


 * Sign, in astrology, often used to mean the Sun sign
 * Sign or signing, in communication, refers to communicating via hand gestures, such as sign language.
 * Signedness, in computing, the digits where one bit among them tells the number is either negative or non-negative are called signed, otherwise unsigned. See also signed number representation
 * Sign, in divination and religion, an omen, an event or occurrence believed to fortell the future
 * Sign, in ontology and spirituality, a coincidence; see synchronicity
 * Sign (linguistics), a combination of a concept and a sound-image described by Ferdinand de Saussure
 * Sign, in mathematics, whether a number is negative or positive
 * Sign, in biology, an indication of some living thing's presence
 * Medical sign, in medicine, objective evidence of the presence of a disease or disorder, as opposed to a symptom, which is subjective
 * Sign (semiotics), the basic units of meaning
 * Information sign, notice that instruct, advise, inform or warn people
 * Traffic sign, signs that instruct drivers; see also stop signs, speed limit signs, cross walk signs
 * Sign, in a writing system, a basic unit. Similar terms which are more specific are character, letter or grapheme
 * Commercial signage, including flashing signs, such as on a retail store, factory, or theatre
 * Signature, in history, a handwritten depiction observed on a document to show authorship and will