sign, early indication, omen
この報道は何の前兆だろうか。
What could this report be a sign of?
彼の怠惰は将来に対する悪い前兆だった。
His laziness was a bad omen for the future.
あの雲は雨の前兆だ。
Those clouds are a sign that rain is on the way.
事が起こる時は前兆があるものだ。
There are usually signs before something happens.
この風は嵐の前兆だ。
This wind is a sign of an approaching storm.