What is a key word from The Giver starting with the letter "u"?

A key word that starts with the letter “u” is “usages.”

Usage, or word use, is very important to Jonas’s community. Part of Sameness is ensuring people use proper language to describe things. Precise language is considered one of the most important aspects of daily life.

Lily explains she felt uncomfortable when she met a group from another community who knew different usages than her group:

Lily frowned. "I felt strange. Because their methods were different. They were learning usages that my group hadn't learned yet, so we felt stupid" (Chapter 1). 

The importance of proper word use is reinforced by the story told about Asher at the Ceremony of Twelve. He used the wrong word as a toddler and he was beaten until he used the right one. 

The other Threes, including Jonas, had laughed nervously. "Snack!" they corrected. "You meant snack, Asher!" But the mistake had been made. And precision of language was one of the most important tasks of small children. Asher had asked for a smack (Chapter 7).

Asher stopped talking for a time after that, but eventually did learn to use the right word. Consequences in the community are harsh, because conformity is the goal. 

Precision of language is considered important to avoiding lying, or making anyone uncomfortable. For example, Jonas was once scolded for saying he was starving. They explained to him that he was just hungry, and he would never be starving. No one in the community will ever be starving.

The community still remembers words that no longer have meaning to them. For example, Jonas asks his parents if they love him after experiencing love in a memory. His parents tell him he has used a worthless and imprecise word that has no meaning.