Know how to use "fewer" and "less"? Find out.
(YA-, after Unix's yacc - Yet Another Compiler-Compiler) A humorous allusion often used in titles to acknowledge that the topic is not original, though the content is. As in "Yet Another AI Group" or "Yet Another Simulated Annealing Algorithm". If used of others' work, it describes something of which there are already far too many.
In hackish acronyms the "YA" prefix almost invariably expands to Yet Another, e.g. YABA, YAUN.