The relationship between speech sounds and the meanings they represent in the languages of the world is, for the most part, an arbitrary one. The Swiss linguist de Saussure regarded the linguistic sign as composed of signifier (sound image) and signified (referent). In his view, there is no inherent relation between the two. A building we live in with our family is called house in English, maison in French, dom in Russian, casa in Spanish. If the relationship between speech sounds and meanings were motivated (i.e., not arbitrary), the words in these languages that stand for the same thing would sound the same or similar, and then people would not need to learn foreign languages.

　 Admittedly, there are a few words in most languages that are onomatopoetic --- words of which the sounds supposedly imitate the sounds of nature. This seems to contradict arbitrariness. Nevertheless, when these words of different languages are compared, it is found that they still sound different. The English the word tick tock is equivalent to the Chinese word dida, buzz to wengweng. In English, cockadoodledoo represents the rooster's crow, but in Russian, kukuriku, both different from the Chinese expression. Based on these observations, we can say that all human languages are conventional. Most animal communications are iconic. A bee dance, for example, rather directly represents its subject matter, because a direct connection exists between the number and direction of the gyrations and the sources of nectar.