An academic grade issued by certain educational institutions. Slightly better than an A. / (slang) The highest possible rating.

Alphabetical order; lexical order. / From beginning to the end. / Over the entirety; completely.

(British) Any of a set of street maps of most British towns and cities; properly the Geographer's A–Z Street Atlas. / (uncountable) All facts related to a subject

(law) A legal standard for deciding the outcome of a criminal charge, requiring evidence that is sufficient to eliminate any doubts that a reasonable person might entertain about whether a claim is more likely to be true than not.

A-sharp.

(emphatic) holy crap.

Abbreviation of account; account current. / Initialism of air conditioning.

The primary plot of a piece of literature, television, etc., contrasted with the secondary B plot.

(education) A grade lower than "A" and higher than "B plus".

(medicine) Of a blood type within the ABO and Rh blood grouping system. Blood type A negative has a phenotype of "A" and a Rhesus system classification of negative.