During his presentation, he lost his voice from nervousness.

lost 是动词 lose 的过去式，lose 的意思是"失去、丧失"。 his 是代词 he 的所有格形式，表示"他的"。 voice 的意思是"声音"，指人说话或唱歌时发出的声音。 lost his voice 是一个固定短语，字面意思是"失去了他的声音"，实际指"突然说不出话"或"失声"，通常是由于过度用嗓、紧张或生病导致的暂时性失声。