Since functionalism treats language as a tool designed and perfected by humans to serve their needs, it understands function as a purpose-oriented property of linguistic structures: it is a way of achieving a communicative aim by linguistic means. Language is fine-tuned to optimise communication, which means, among other things, that the natural conflict between the speaker’s needs (encoding and sending linguistic messages at a low cost) and the listener’s needs (receiving and decoding messages without unnecessary effort) must be resolved. Languages maintain a delicate balance between ease of production and ease of perception. For example, precise enunciation is expensive in terms of articulatory effort and neuromuscular control, but if the speaker tries to reduce this cost excessively by sacrifying precision, the result may be the listener’s failure to understand the message. Since having to repeat a sentence twice is usually costlier than saying it once with sufficient clarity, the speaker has to anticipate any undesirable difficulties at the listener’s end, and the tendency to favour ease of articulation is mitigated by those anticipations.

Language change can make life minimally easier for the speaker or the listener. Sound changes are often classified into “lenitions” (weakenings) and “fortitions” (strengthenings). Weakenings consist in reducing articulatory effort (and the acoustic prominence of speech sounds), while strengthenings involve increased effort (and acoustic prominence). In this dualist interpretation, weakenings are speaker-oriented, while strengthenings are listener-oriented. Any change has a purpose, and therefore a functional significance – all that needs to be determined is its orientation: cui bono? More.

See: Language Evolution