Word formation refers to the creation of new words.
Example
Blending (smog), loan words from other languages (parasol), and acronyms (scuba) are all examples of ways new words are formed.
In the classroom
As a way of raising awareness of the processes involved in the creation of new words in English, learners can be encouraged to create new words of their own using blending, changing the way words are used, e.g. making nouns into new verbs, or borrowing words from their own languages.
Further links:
https://www.teachingenglish.org.uk/article/new-words-english
https://www.teachingenglish.org.uk/article/how-new-words-are-created
https://www.teachingenglish.org.uk/article/dictionaries-lexicography-language-learning