Think of words like puzzle pieces. When we speak or write, we connect these pieces together to make clear sentences. But sometimes, we use language shortcuts that combine two or more puzzle pieces into one. This is called fusion in linguistics.
For example, the word "won't" is a fusion of "will" and "not." It means the same thing as "will not" but is a quicker and easier way to say it. Another example is "ain't," which is a fusion of "am not" or "is not" or "are not."
Fusion is not only limited to contractions. In some languages, such as Spanish, fusion occurs in verb conjugation, where adding specific letters to the end of the verb stem changes the tense and subject.
In conclusion, fusion is a way that we simplify language by combining two or more puzzle pieces into one. It can happen in contractions, verb conjugations, and many other areas of language study.