Suddenly
Sudden
adverb, な adjective, の adjective
When something happens with a sudden nature, it happens... suddenly.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
突然やって来る
to suddenly come along
突然倒れる
to suddenly collapse
突然起こる
to suddenly occur
突然現れる
to suddenly appear
その時は、突然やって来ました。
That time came suddenly.
突然の大雨で、ビショビショになってしまった。
Due to a sudden heavy rain, I got completely soaked.
突然のことだったので、何が何だか分かりませんでした。
It was so sudden that I did not know what was what.
突然、猫のお化けが台所に現れて、「ニャーニャーソング」を歌い始めたんだ。
Suddenly the ghost of a cat showed up in my kitchen and started singing the mew-mew song.
病院から突然、何百人もの赤毛の人々が出てきました。その中の一人に話しかけると、赤毛の人に対する大きな医学実験があったと言われました。
Suddenly, hundreds of red-haired people came out of the hospital. When I spoke to one of them, I was told there had been a large medical experiment involving red-haired individuals.