A counter/noun meaning a wave or occurrence in a series (e.g. 'the first wave', 'the second wave'); used to count or label repeated occurrences or stages of events.
専門家は第三波が来る可能性について話している。
Experts are talking about the possibility of a third wave coming.
流行の第二波に備えて、医療体制を強化した。
We strengthened the healthcare system in preparation for the second wave of the outbreak.
第一波の影響は収まりつつあるが、次の波に注意が必要だ。
The impact of the first wave is settling, but caution is needed for the next wave.