In The Giver by Lois Lowry, "precision of language" is required and strictly enforced in Jonas's community. The community regulates precise language in order to eliminate misunderstandings or room for interpretation. Jonas's community prizes pragmatism and absolutely equality. "Precise language" reinforces their pragmatic, uniform approach to live. Imprecise or emotional language could highlight differences or matters of opinion, which the community is strongly against.
For Jonas, this makes processing his new experiences much more difficult. As the Receiver, his experiences are meant to be felt rather than clinically described. Feelings, however, require ambiguity in their very nature. Love, hatred, longing, and friendship are all very imprecise concepts. While Jonas explores all of these and more during his Receiver trainings, he cannot describe them while maintaining the expectation of precise language.
This makes it more difficult for Jonas to relate to others as he develops throughout the novel. At one point, Jonas says that he loves his family. Rather than returning his affections, his family chides his use of imprecise language. According to the community, he should have used a term like "I enjoy you," as "I love you," is far too ambiguous. This directly prohibits Jonas from truly expressing himself, which leads to his growing dissatisfaction with the community.