A dialect is a form of a language spoken by a group of people. People who live in the same place may share a dialect; this is called a "regiolect". People who are similar in some other way, such as social class, may share a dialect.
There is no absolute difference between a dialect and a language. British English and American English are different standard dialects of English. They differ slightly in spelling, pronunciation, and vocabulary. However, they are "mutually intelligible", which means people who speak either variety understand the other.
Deciding if something is a language or a dialect is sometimes a political decision as a way to make minority groups assimilate or become part of a nation's larger culture. The linguist Max Weinreich once joked that "a language is a dialect with an army and a navy."
Japanese and the Okinawan language are related, as they are Japonic languages, but they are not mutually intelligible. When Japan took over Okinawa during the Meiji Era, the Japanese government called the Okinawan language a dialect of Japanese. This was used to forbid Okinawans from speaking Okinawan and to force them to Japanese.
Catalan and Galician used to be considered as dialects of Spanish but are now recognized as languages. They are about as near to Portuguese and to Occitan, respectively, as they are to Spanish.
Hindi and Urdu are called different languages today, but they used to be the same language, Hindustani. After Pakistan became separate from India, Hindustani became called Urdu in Pakistan and Hindi in India. However, speakers of both can understand each other if they are using everyday speech. The two languages use different writing systems, but writing systems are not an accurate way to decide if languages are related.
English is definitely a language, but it once was Anglo-Saxon, a dialect of Old Saxon.
Chinese is called a language, but has hundreds of dialects, such as Mandarin, Cantonese, Wu, and Hokkien. Many of them are not mutually intelligible.
In past times, travel was difficult and so dialects developed in quite small regions. In Britain, there were dialects in the different parts of the country, and traces can stiill be heard today. The Romance languages were dialects of Latin that separated in that way.
Differences in dialects can be:
- words: people in England to church, but in Scotland, people go to kirk.
- Pronunciation: the r of letters is silent in most of England but is pronounced by most of the United States.
- grammar: instead of I dived, some people say I dove.
In India, there are scores of dialects of Hindi language like Rajasthani, Bhojpuri, Chhattisgarhi, Magadhi, Haryanvi and others. Moreover,people whose native language is Hindi, may or maynot treat it as their mother tongue.
With certain kinds of birds, people have noticed that their singing is different in different geographical areas. They have called these variations dialects. Similar observations have been done with Orcas.