The general attributes of writing systems can be placed into broad categories such as alphabets, syllabaries, or logographies. Any particular system can have attributes of more than one category. In the alphabetic category, there is a standard set of letters (basic written symbols or graphemes) of consonants and vowels that encode based on the general principle that the letters (or letter pair/groups) represent speech sounds. In a syllabary, each symbol correlates to a syllable or mora. In a logography, each character represents a word, morpheme, or other semantic units. Other categories include abjads, which differ from alphabets in that vowels are not indicated, and abugidas or alphasyllabaries, with each character representing a consonant–vowel pairing. Alphabets typically use a set of 20-to-35 symbols to fully express a language, whereas syllabaries can have 80-to-100, and logographies can have several hundreds of symbols.
Most systems will typically have an ordering of its symbol elements so that groups of them can be coded into larger clusters like words or acronyms (generally lexemes), giving rise to many more possibilities (permutations) in meanings than the symbols can convey by themselves. Systems will also enable the stringing together of these smaller groupings (sometimes referred to by the generic term 'character strings') in order to enable a full expression of the language. The reading step can be accomplished purely in the mind as an internal process, or expressed orally. A special set of symbols known as punctuation is used to aid in structure and organization of many writing systems and can be used to help capture nuances and variations in the message's meaning that are communicated verbally by cues in timing, tone, accent, inflection or intonation. A writing system will also typically have a method for formatting recorded messages that follows the spoken version's rules like its grammar and syntax so that the reader will have the meaning of the intended message accurately preserved.
Chinese characters (漢字) are morpho-syllabic. Each one represents a syllable with a distinct meaning, but some characters may have multiple meanings or pronunciations
Writing systems are distinguished from other possible symbolic communication systems in that a writing system is always associated with at least one spoken language. In contrast, visual representations such as drawings, paintings, and non-verbal items on maps, such as contour lines, are not language-related. Some symbols on information signs, such as the symbols for male and female, are also not language related, but can grow to become part of language if they are often used in conjunction with other language elements. Some other symbols, such as numerals and the ampersand, are not directly linked to any specific language, but are often used in writing and thus must be considered part of writing systems.
Every human community possesses language, which many regard as an innate and defining condition of humanity. However, the development of writing systems, and the process by which they have supplanted traditional oral systems of communication, have been sporadic, uneven and slow. Once established, writing systems generally change more slowly than their spoken counterparts. Thus they often preserve features and expressions which are no longer current in the spoken language. One of the great benefits of writing systems is that they can preserve a permanent record of information expressed in a language.
All writing systems require:
at least one set of defined base elements or symbols, individually termed signs and collectively called a script;
at least one set of rules and conventions (orthography) understood and shared by a community, which assigns meaning to the base elements (graphemes), their ordering and relations to one another;
at least one language (generally spoken) whose constructions are represented and can be recalled by the interpretation of these elements and rules;
some physical means of distinctly representing the symbols by application to a permanent or semi-permanent medium, so they may be interpreted (usually visually, but tactile systems have also been devised).