Fluency (also called volubility and eloquency) refers to continuity, smoothness, rate, and effort in speech production. It is also used to characterize language production, language ability or language proficiency.
In speech language pathology it means the flow with which sounds, syllables, words and phrases are joined when speaking quickly, where fluency disorder has been used as a collective term for cluttering and stuttering.
An endangered language or moribund language is a language that is at risk of disappearing as its speakers die out or shift to speaking other languages. Language loss occurs when the language has no more native speakers and becomes a "dead language". If no one can speak the language at all, it becomes an "extinct language". A dead language may still be studied through recordings or writings, but it is still dead or extinct unless there are fluent speakers left. Although languages have always become extinct throughout human history, endangered languages are currently dying at an accelerated rate because of globalization, mass migration, cultural replacement, imperialism, neocolonialism and linguicide (language killing).
Language shift most commonly occurs when speakers switch to a language associated with social or economic power or one spoken more widely, leading to the gradual decline and eventual death of the endangered language. The process of language shift is often influenced by factors such as globalisation, economic authorities, and the perceived prestige of certain languages. The ultimate result is the loss of linguistic diversity and cultural heritage within affected communities. The general consensus is that between 6,000 and 7,000 languages are currently spoken. Some linguists estimate that between 50% and 90% of them will be severely endangered or dead by the year 2100. The 20 most common languages, each with more than 50 million speakers, are spoken by 50% of the world's population, but most languages are spoken by fewer than 10,000 people.
Speech disorders, impairments, or impediments, are a type of communication disorder in which normal speech is disrupted. This can mean fluency disorders like stuttering and cluttering. Someone who is unable to speak due to a speech disorder is considered mute. Speech skills are vital to social relationships and learning, and delays or disorders in developing these skills can impact individuals' function. For many children and adolescents, this can present as issues with academics. Speech disorders affect roughly 11.5% of the US population, and 5% of the primary school population. Speech is a complex process that requires precise timing, nerve and muscle control, and as a result is susceptible to impairments. A person who has a stroke, an accident or birth defect may have speech and language problems.