Toy play, book reading, and mealtimes present distinctive types of opportunities for the introduction of rare words.
Toy play is the least complicated conversational setting because it involves just the [parent] and the child and there are objects in the immediate context to refer to and few intervening distrations.
Book reading, in contrast, is a more complex vocabulary situation because there are two sources of words: the words in the book and the words spoken by the parent.
Mealtimes are also complex, but for another reason: They often provide a variety of conversational partners.
Source: Beginning Literacy with Language, by David K. Dickinson and Patton O. Tabors, Brookes Publishing, pg. 97