aB

Ab is a two-letter combination with diverse meanings in language, science, and technology. Depending on context, ab or AB can be a prefix, a code, or a symbol in various fields.

In linguistics and word formation, ab- is a Latin prefix meaning away from or from. It is seen in English derivatives such as abduct, abstain, and abstract. In some contexts abs- occurs before certain consonants due to assimilation.

In codes and classifications, AB is used as an abbreviation for Alberta, a Canadian province (postal code AB). In biology and medicine, Ab is commonly used to denote an antibody, an antigen-binding protein central to the immune response. The AB blood group denotes individuals with both A and B antigens.

In computing, ab is the ApacheBench tool used to benchmark HTTP servers, often invoked on the command line as ab. In music, AB form refers to a two-section structure, with a contrasting B section following an initial A.

Other uses include AB as a common two-letter string in examples of concatenation and pattern notation.