This book introduces definitions of 18 inventions that are essential to our daily lives. Throughout the book, young readers will encounter relative pronoun clauses using that and which, which provide additional information about the nouns they precede. Readers will also explore three different uses of that: as a demonstrative pronoun, a noun clause connector, and a relative pronoun. Additionally, they will learn two distinct roles of which: as a question word and a relative pronoun. By the end of the book, readers will be able to identify whether a sentence is complete or incomplete, and define the role of each that and which in context.