basic units of sound in a language are called
Phoneme A phoneme (/ˈfoʊniːm/) is one of the units of sound (or gesture in the case of sign languages, see chereme) that distinguish one word from another in a particular language. For example, in most dialects of English, the sound patterns /θɪn/ (thin) and /dɪn/ (din) are two separate words distinguished by the substitution of one phoneme, /θ/, for another phoneme, /d/. (Two words like this that differ in meaning through a contrast of a single phoneme form what is called a minimal pair). In many other languages these would be interpreted as exactly the same set of phonemes (i.e. /θ/ and /d/ would be considered the same).
Metric system In its modern form, it consists of a set of electromechanical base units including metre for length, kilogram for mass, second for time and ampere as an electrical unit, and a few others, which together with their derived units, can measure any useful quantity. Metric system may also refer to other systems of related base and derived units defined before the middle of the 20th century, some of which are still in limited use today.