What is the meaning of ב?

The second letter of the Aramaic alphabet.

The numeral 2 in Aramaic numbering.

Bet, beth, vet: the second letter of the Hebrew alphabet, after א and before ג.

The numeral 2 in Hebrew numbering.

Initialism of בֵּינַיִם, used to indicate that a term originates from the third layer of the Hebrew language: Medieval Hebrew

the second letter of the Yiddish alefbeys

Source: wiktionary.org