David Crystal in the context of Linguistics

Phonaesthetics (also spelled phonesthetics in North America) is the study of the beauty and pleasantness associated with the sounds of certain words or parts of words. The term was first used in this sense, perhaps by J. R. R. Tolkien, during the mid-20th century and derives from Ancient Greek φωνή (phōnḗ) 'voice, sound' and αἰσθητική (aisthētikḗ) 'aesthetics'. Speech sounds have many aesthetic qualities, some of which are subjectively regarded as euphonious (pleasing) or cacophonous (displeasing). Phonaesthetics remains a budding and often subjective field of study, with no scientifically or otherwise formally established definition; today, it mostly exists as a marginal branch of psychology, phonetics, or poetics.

More broadly, the British linguist David Crystal has regarded phonaesthetics as the study of "phonaesthesia" (i.e., sound symbolism and phonesthemes): that not just words but even certain sound combinations carry meaning. For example, he shows that English speakers tend to associate unpleasantness with the sound sl- in such words as sleazy, slime, slug, and slush, or they associate repetition lacking any particular shape with -tter in such words as chatter, glitter, flutter, and shatter.

International scientific vocabulary (ISV) is the set of scientific and specialized words that are in current use in several modern languages. Although the language of origin of ISV may or may not be certain, they are used translingually, whether in naturalized, loanword, or calque forms.

The name "international scientific vocabulary" was first used by Philip Gove in Webster's Third New International Dictionary (1961). As noted by David Crystal, science is an especially productive field for new coinages. It is also especially predisposed to immediate translingual sharing of words owing to its very nature: scientists working in many countries and languages, reading each other's latest articles in scientific journals (via foreign language skills, translation help, or both), and eager to apply any reported advances to their own context.