Which vocabulary word is easiest for a child to learn when utilizing principles of neighborhood density?

The word "cat" is the easiest for a child to learn when considering principles of neighborhood density. Neighborhood density refers to how many words are phonetically similar to a word and how closely related these words are in terms of their meanings and phonological structures.

"Cat" has a high neighborhood density because it rhymes with and is similar in sound to several other common words, such as "hat," "bat," and "mat." This phonological similarity can aid in word learning as children can make connections between "cat" and these other familiar words, thereby reinforcing their understanding of the sound structure of similar words.

Additionally, "cat" is a concrete noun referring to a familiar animal that many children encounter in their daily lives, making it more relatable and memorable. Words that belong to high-frequency categories—such as animals, objects, or actions—tend to be learned more easily as they are often part of a child's everyday experiences and interactions.

In contrast, the other options, while they may be common words, do not have the same level of neighborhood density or the same strong concrete association that enhances learning through familiarity and reinforcement of related terms.