noun
The numeral zero; used in counting, scores, temperatures, and mathematical contexts. The 〇 form is especially used with kanji numerals.
See also: 零 (れい)
テストの点数はゼロだった。
My test score was zero.
気温がゼロ度まで下がった。
The temperature dropped to zero degrees.
noun
nothing; zilch
Informal use meaning 'nothing at all' or 'absolutely nothing'. Often used in casual speech.
冷蔵庫には何もない。ゼロだ。
There's nothing in the fridge. Zilch.
零 (れい) is the native Japanese reading for the kanji 零, used in formal or traditional contexts, while ゼロ is the loanword from English and more common in everyday use.
Loanword from English 'zero', adopted into Japanese as ゼロ. The kanji forms ０, 〇, and 零 are used to represent the numeral zero in writing.