In mathematics, particularly in set theory, the beth numbers are a certain sequence of infinite cardinal numbers, conventionally written ℶ 0, ℶ 1, ℶ 2, ℶ 3, … {\displaystyle \beth _{0},\ \beth _{1},\ \beth _{2},\ \beth _{3},\ \dots }, where ℶ {\displaystyle \beth } is the second Hebrew letter. Wikipedia