Which of the following is an example of a compound word?

A compound word is formed when two or more words are combined to create a new word with its own meaning. In the case of "household," it combines the words "house" and "hold," referring to a group of people living together in a single home. This formation illustrates how the meanings of the individual components contribute to a new concept related to living arrangements.

The other choices provided are simple words that stand alone and do not consist of two or more combined words. "Chair," "book," and "pencil" are all singular nouns that convey specific objects without any additional components. They cannot be broken down into simpler parts that create a different concept, showcasing the distinct characteristic of a compound word.