structural:expansion, linguistic:voice_change, linguistic:translation
Sounds and symbols

Depending on modality, language structure can be based on systems of sounds (speech), gestures (sign languages), or graphic or tactile symbols (writing). The ways in which languages use sounds or signs to construct meaning are studied in phonology.

Sounds as part of a linguistic system are called phonemes. Phonemes are abstract units of sound, defined as the smallest units in a language that can serve to distinguish between the meaning of a pair of minimally different words, a so-called minimal pair. In English, for example, the words bat and pat form a minimal pair, in which the distinction between /b/ and /p/ differentiates the two words, which have different meanings. However, each language contrasts sounds in different ways. For example, in a language that does not distinguish between voiced and unvoiced consonants, the sounds and (if they both occur) could be considered a single phoneme, and consequently, the two pronunciations would have the same meaning. Similarly, the English language does not distinguish phonemically between aspirated and non-aspirated pronunciations of consonants, as many other languages like Korean and Hindi do: the unaspirated /p/ in spin and the aspirated /p/ in pin are considered to be merely different ways of pronouncing the same phoneme (such variants of a single phoneme are called allophones), whereas in Mandarin Chinese, the same difference in pronunciation distinguishes between the words 'crouch' and 'eight' (the accent above the á means that the vowel is pronounced with a high tone).

All spoken languages have phonemes of at least two different categories, vowels and consonants, that can be combined to form syllables. As well as segments such as consonants and vowels, some languages also use sound in other ways to convey meaning. Many languages, for example, use stress, pitch, duration, and tone to distinguish meaning. Because these phenomena operate outside of the level of single segments, they are called suprasegmental. Some languages have only a few phonemes, for example, Rotokas and Pirahã language with 11 and 10 phonemes respectively, whereas languages like Taa may have as many as 141 phonemes. In sign languages, the equivalent to phonemes (formerly called cheremes) are defined by the basic elements of gestures, such as hand shape, orientation, location, and motion, which correspond to manners of articulation in spoken language.

Writing systems represent language using visual symbols, which may or may not correspond to the sounds of spoken language. The Latin alphabet (and those on which it is based or that have been derived from it) was originally based on the representation of single sounds, so that words were constructed from letters that generally denote a single consonant or vowel in the structure of the word. In syllabic scripts, such as the Inuktitut syllabary, each sign represents a whole syllable. In logographic scripts, each sign represents an entire word, and will generally bear no relation to the sound of that word in spoken language.

Because all languages have a very large number of words, no purely logographic scripts are known to exist. Written language represents the way spoken sounds and words follow one after another by arranging symbols according to a pattern that follows a certain direction. The direction used in a writing system is entirely arbitrary and established by convention. Some writing systems use the horizontal axis (left to right as the Latin script or right to left as the Arabic script), while others such as traditional Chinese writing use the vertical dimension (from top to bottom). A few writing systems use opposite directions for alternating lines, and others, such as the ancient Maya script, can be written in either direction and rely on graphic cues to show the reader the direction of reading.

In order to represent the sounds of the world's languages in writing, linguists have developed the International Phonetic Alphabet, designed to represent all of the discrete sounds that are known to contribute to meaning in human languages.