Dialect

A dialect is a regional or social variety of a language. It can differ from the standard form in vocabulary, grammar and pronunciation, and its speakers usually understand the standard form too. The line between a dialect and a separate language is often a matter of politics and history rather than linguistics alone, which is why researchers also use the broader term language variety.

A dialect means more than pronunciation

A dialect is not only a different accent. It can bring different words for everyday objects, different verb forms and different sentence patterns. Modern Standard Arabic, for example, is the formal written standard, while the spoken forms used in everyday life vary by country and city. Swiss German is a similar case: many people in Switzerland speak regional dialects that differ from the German taught in schools. The distinction matters because a locale can name a language and region, but a dialect is a variety of speech that the locale may not capture.

Dialects raise speech recognition error rates

Recognizers are usually trained on the standard form and on the speech that is easiest to collect. A 2025 study reports that error rates for Arabic speech rise sharply on dialectal and accented speech, compared with Modern Standard Arabic, because of linguistic mismatch and scarce labeled data ¹. Older work shows the same pattern. On the 1996/97 NIST CallHome task for Egyptian Colloquial Arabic, the best word error rate obtained in those evaluations was 61 percent ².

Spanish shows the variation on a smaller scale. In a 2026 test of YouTube's automatic Spanish captions, Argentinian Spanish had the highest overall word error rate of the dialects tested, at 24 percent ³, and Mexican Spanish had an overall word error rate of 18 percent ⁴. The Mexican recordings came from a different dataset, so the comparison is a warning, not a precise ranking, and it measures a captioning system rather than a dictation app.

A concrete example: the same language, two dialects

Suppose you dictate in Spanish, but you speak the Spanish of Buenos Aires, with its own vocabulary and intonation. A recognizer trained mostly on other varieties may choose words that are common in those varieties and miss some of yours. The output is still Spanish, which makes the errors easy to overlook. Read a short test passage in your own dialect before you trust a tool for a long document.

Why it matters for dictation and typing

For dictation, a dialect is a reason to choose the closest locale and to test before you commit. A locale for a country is not always a locale for your dialect, and some languages have few dialect-specific models. Our guide to Spanish speech to text explains how the Spanish variants differ across platforms, and the guide to Arabic speech to text covers the dialect problem for Arabic. The question on which Arabic dialects speech to text handles lists the practical options.

A dialect and an accent can both affect recognition, but they are not the same. An accent is how someone pronounces a language. A dialect is a variety with its own words and grammar, and it can come with a different accent too.

Related terms

• Accent: the pronunciation of a speaker, which can differ from the dialect's vocabulary and grammar.
• Locale: the language and region setting a device uses.
• Non-native speech: speech in a second language, which can also be recognized less accurately.
• Word error rate (WER): the usual measure behind the dialect figures above.

Guides and questions that cover it

• Guide: Spanish speech to text and talk to text.
• Guide: Arabic speech to text and right-to-left dictation.
• Question: which Spanish should you use for dictation?
• Question: which Arabic dialects does speech to text handle?
• Overview: dictation languages, accents and voice translation.