Final answer:
The linguistics area that deals with letters and sounds, such as those considered when naming the Dasani bottled water brand, is known as phonology.
Step-by-step explanation:
When linguists aided the Coca-Cola Company in naming their new Dasani bottled water brand, they focused on the sounds that letters make, such as the soothing sound of the recurring 'a'. The aspect of linguistics that deals with letters and sounds is known as phonology. Phonology is the study of how sounds are organized and used in natural languages. Neither syntax (the arrangement of words and phrases to create well-formed sentences), semantics (the meaning of words and sentences), nor semiotics (the study of signs and symbols and their use or interpretation) pertains to the actual sounds of the language but rather to other linguistic aspects. The selection of Dasani as a brand name with its soothing 'a' sounds is a practical application of phonological principles in marketing.