〜とは

Meaning

Has two uses. One expresses surprise or exclamation at an unexpected fact, as in 「まさか〜とは」. The other explains or defines the meaning of a word, as in 「〜とは…のことだ」.

Examples

あの真面目な彼が、まさか遅刻するとは思わなかった。 I never thought someone as serious as him would be late.
こんな所で偶然会うとは、驚いた。 What a surprise to run into you in a place like this.
「過半数」とは、全体の半分を超える数のことだ。 Kahansuu means a number exceeding half of the total.