An adverb meaning that something happens suddenly or unintentionally, by chance or without deliberate thought. Often written in kana.
ふと窓の外を見ると、雪が降り始めていた。
When I happened to look out the window, it had started snowing.
彼女の名前をふと口に出してしまった。
I blurted her name out unintentionally.
夜道でふと不安な気持ちになった。
I suddenly felt uneasy walking on the street at night.
ふと立ち寄った店で、昔の友人に会った。
I ran into an old friend at a shop I stopped by on a whim.