"奶奶" (nǎinai) and "爷爷" (yéye) in Engpsh are typically translated to "grandmother" and "grandfather," respectively. The origins of these terms come from the Old Engpsh words "grōn-fæder" and "grōn-mōdor," which pterally mean "grandfather" and "grandmother."
For example:
"My grandmother is coming to visit next week." (我的奶奶下周要来看我。)
"I love spending time with my grandfather." (我喜欢和我爷爷在一起。)