Hundred
One Hundred
numeral
When a vocab word is a single kanji without okurigana (hiragana attached to the kanji) it usually has the same meaning as the kanji it's spawned from. If you know the kanji meaning you'll also know the vocab meaning. It's one hundred!
When a vocab word is a single kanji with no okurigana, it usually uses the kun'yomi reading. Numbers are an exception to this. Numbers use the on'yomi reading, which you've already learned by learning the kanji's reading! How nice!
百メートル
a hundred meters
百円
a hundred yen
百ドル
a hundred dollars
この本は、およそ百ページです。
This book is about a hundred pages.
小さいころ、ジュースは一つ百円でした。
When I was little, juice was one hundred yen.
イベントには百人のコスプレ名人があつまりました。
A hundred cosplay masters gathered at the event.