Numeral
ごじゅう
かいてんずしで、五十さらたべた。
I ate fifty plates at conveyer belt sushi.
ある天才いしは、たったの五十えんでつうふうをなおすちりょうほうをはつめいしました。
One genius doctor invented a cure for gout for only 50 yen.
ほぼ五十ねんかんあなたのことがすきでしたが、きのうさめました。
I loved you for nearly fifty years, but yesterday that ended.
What happens when you have ten five times? You get fifty!
This is a jukugo word, which usually means on'yomi readings from the kanji. That's the case for this word too, which means you should already know how to read this word.