The vocabulary of preschool children is the subject of this final thesis. The paper aims to show the importance of vocabulary development in preschool children and how this development can be encouraged. Language acquisition begins already in the second trimester of pregnancy, while the child in the womb listens and recognizes sounds from the environment. Starting school, therefore, around the seventh year of a child's life, the phase of concrete thought operations begins, and morphological and syntactic knowledge becomes automatic around the age of eleven during the phase of abstract thinking. It should be emphasized that there are generalities related to the process of language acquisition, and they are that language acquisition will depend on the number of children in the family, on the child's exposure to the language, on the social environment in which the child grows up, on the peers with whom the child establishes first communications. The process of language acquisition is influenced by parents, educators, and the immediate and wider social community. The process of vocabulary development in preschool age is characterized by the gradual and individual expansion of the child's vocabulary. Children first acquire a passive vocabulary consisting of words they understand, while the active use of words and expressions develops gradually. Preschool children's vocabulary covers a wide range of words, including more concrete concepts such as colors, shapes, and animals and abstract concepts such as feelings, time, and space. The development of the preschool child's vocabulary is encouraged through various activities. Reading children's books with a rich vocabulary, word games, dialogue and conversation with children, and exploring the environment are important incentives for vocabulary development. These activities allow children to get to know new words, understand their meaning, and apply them in a practical context. Parents and guardians must recognize their role in supporting the vocabulary development of preschool children. Providing a rich language environment, encouraging conversation, asking questions, and encouraging vocabulary-stimulating games can contribute to a child's successful language development.