An L-system or Lindenmayer system is a parallel rewriting system, namely a variant of a formal grammar

Formal grammar

A formal grammar is a set of formation rules for strings in a formal language. The rules describe how to form strings from the language's alphabet that are valid according to the language's syntax...

, most famously used to model the growth processes of plant development, but also able to model the morphology of a variety of organisms. A L-system consists of an alphabet

Alphabet

An alphabet is a standard set of letters—basic written symbols or graphemes—each of which represents a phoneme in a spoken language, either as it exists now or as it was in the past. There are other systems, such as logographies, in which each character represents a word, morpheme, or semantic...

 of symbols that can be used to make string

String (computer science)

In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set or alphabet....

s, a collection of production rule

Production rule

Production rule may refer to:*For production rules used in business rule engines, cognitive modeling and artificial intelligence, see production system*For production rules that expand nodes in formal grammars, see formal grammar-See also:...

s which expand each symbol into some larger string of symbols, an initial "axiom

Axiom

In traditional logic, an axiom or postulate is a proposition that is not proven or demonstrated but considered either to be self-evident or to define and delimit the realm of analysis. In other words, an axiom is a logical statement that is assumed to be true...

" string from which to begin construction, and a mechanism for translating the generated strings into geometric structures.