A suggested defining property of human LANGUAGE (contrasting with the properties of other SEMIOTIC systems) whereby LINGUISTIC FORMS are said to lack any physical correspondence with the entities in the world to which they refer. For example, there is nothing in the word table which reflects the shape, etc., of the thing. The relationship between sound and meaning is said to be arbitrary – or ‘conventional’, as classical tradition puts it. By contrast, some words in a language may be partly or wholly ICONIC, i.e. they do reflect properties of the non-linguistic world, e.g. onomatopoeic expressions, such as splash, murmur, mumble.