In logic, mathematics, computer science, and linguistics, a formal language is a set of strings whose symbols are taken from a set called "alphabet".
The alphabet of a formal language consists of symbols that concatenate into strings (also called "words"). Words that belong to a particular formal language are sometimes called well-formed words. A formal language is often defined by means of a formal grammar such as a regular grammar or context-free grammar.
In logic, a reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to refer to the second object. It is called a name for the second object. The next object, the one to which the first object refers, is called the referent of the first object. A name is usually a phrase or expression, or some other symbolic representation. Its referent may be anything – a material object, a person, an event, an activity, or an abstract concept.
References can take on many forms, including: a thought, a sensory perception that is audible (onomatopoeia), visual (text), olfactory, or tactile, emotional state, relationship with other, spacetime coordinates, symbolic or alpha-numeric, a physical object, or an energy projection. In some cases, methods are used that intentionally hide the reference from some observers, as in cryptography.
Some people do not eat various specific foods and beverages in conformity with various religious, cultural, legal or other societal prohibitions. Many of these prohibitions constitute taboos. Many food taboos and other prohibitions forbid the meat of a particular animal, including mammals (such as rodents), reptiles, amphibians, fish, molluscs, crustaceans and insects, which may relate to a disgust response being more often associated with meats than plant-based foods. Some prohibitions are specific to a particular part or excretion of an animal, while others forgo the consumption of plants or fungi.
Some food prohibitions can be defined as rules, codified by religion or otherwise, about which foods, or combinations of foods, may not be eaten and how animals are to be slaughtered or prepared. The origins of these prohibitions are varied. In some cases, they are thought to be a result of health considerations or other practical reasons; in others, they relate to human symbolic systems.