Sound shifts are regular and predictable changes in the pronunciation of a language's sounds over time. These changes can affect individual sounds, groups of sounds, or entire syllables.

The Great Vowel Shift was a major sound shift that occurred in English between the 15th and 17th centuries. It involved a series of changes in the pronunciation of long vowels, resulting in the modern pronunciation of many English words.

Lexical expansion refers to the process by which new words and phrases are added to a language's vocabulary. This can occur through various mechanisms, such as borrowing from other languages, coinage of new words, and semantic extension.

The word 'computer' was coined in the 20th century to describe electronic devices capable of performing calculations and processing information.

Semantic drift refers to the gradual change in the meaning of a word or phrase over time. This can occur due to various factors, such as cultural shifts, technological advancements, and changes in social norms.

The word 'nice' originally meant 'foolish' or 'stupid' in the 14th century. Over time, its meaning gradually shifted to 'agreeable' or 'pleasant'.

Grammatical evolution refers to the gradual changes in a language's grammatical structures and rules over time. These changes can affect various aspects of grammar, such as word order, verb conjugation, and sentence structure.

The dative case, which was used to indicate the indirect object of a verb, gradually disappeared from English between the 12th and 16th centuries.

Language divergence refers to the process by which languages gradually become more different from each other over time due to factors such as geographic isolation, cultural changes, and linguistic innovations.

The Indo-European Language Family is one of the most widely spoken language families in the world, with languages spoken across Europe, Asia, and parts of Africa. It has undergone extensive divergence, resulting in a wide variety of languages with distinct features.

Language contact refers to the interaction between two or more languages, resulting in mutual influence and changes in their structures, vocabulary, and pronunciation.

English has been heavily influenced by language contact throughout its history, with influences from Latin, French, Norse, and other languages. This has resulted in a rich and diverse vocabulary and a complex grammatical structure.

Language extinction refers to the process by which a language gradually ceases to be spoken and eventually disappears. This can occur due to various factors, such as assimilation, displacement by other languages, and cultural changes.

Ainu is an indigenous language spoken by the Ainu people of Japan. It is facing the threat of extinction due to assimilation and the dominance of Japanese.

Studying the evolution of languages over time presents several challenges, including the lack of written records for many languages, incomplete linguistic data, and the difficulty in reconstructing ancestral languages.