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, or changes in social norms.

All of the given examples are instances of semantic drift. The meanings of the words 'nice', 'awful', and 'gay' have changed significantly over time, acquiring new connotations and associations.

Semantic extension refers to the process of assigning new meanings to existing words or phrases. This can occur through various mechanisms, such as metaphor, metonymy, or generalization.

All of the given examples are instances of semantic extension. The meanings of the words 'mouse', 'table', and 'cloud' have been extended to encompass new concepts and technologies.

A loanword is a word that has been borrowed from another language and incorporated into a new language. Loanwords can be adopted due to cultural exchange, trade, or political influence.

All of the given examples are instances of loanwords. The words 'sushi', 'taco', and 'chai' have been borrowed from Japanese, Spanish, and Hindi, respectively.

Etymology is the study of the historical development of words and their meanings. It involves tracing the origins of words, identifying their root forms, and understanding how their meanings have changed over time.

All of the given examples are instances of etymological research. They involve investigating the historical development and origins of words and their meanings.

Compounding is the process of creating new words by combining existing morphemes. This can be done through various mechanisms, such as affixation, blending, or clipping.

All of the given examples are instances of compounding. The words 'blackbird', 'bookstore', and 'sunflower' are all formed by combining two or more existing morphemes.

Polysemy is the process of assigning different meanings to the same word or phrase depending on the context. This can occur due to various factors, such as historical changes, metaphorical extensions, or regional variations.

All of the given examples are instances of polysemy. The words 'bank', 'head', and 'run' all have multiple meanings that depend on the context in which they are used.

Back-formation is the process of creating new words by altering the pronunciation or spelling of existing words. This can occur when speakers mistakenly derive a new word from an existing word that is perceived to be its root.

All of the given examples are instances of back-formation. The words 'edit', 'burger', and 'selfie' were all created by altering the pronunciation or spelling of existing words.

Blending is the process of creating new words by combining two or more existing words. This can be done by combining the beginnings of two words, the ends of two words, or a combination of both.

All of the given examples are instances of blending. The words 'smog', 'brunch', and 'spork' were all created by combining two or more existing words.