A the 1st letter of the Roman alphabet
AIDS a serious (often fatal) disease of the immune system transmitted through blood products especially by sexual contact or contaminated needles
ADHD condition characterized by behavioral and learning disorders
A.D. in the Christian era
AWOL one who is away or absent without leave
1000 the cardinal number that is the product of 10 and 100
A.M. before noon
ASAP as soon as possible
Abel (Old Testament) Cain and Abel were the first children of Adam and Eve born after the Fall of Man; Abel was killed by Cain
ATP a nucleotide derived from adenosine that occurs in muscle tissue; the major source of energy for cellular reactions
ACTH a hormone produced by the anterior pituitary gland that stimulates the adrenal cortex
9/11 the day in 2001 when Arab suicide bombers hijacked United States airliners and used them as bombs
24/7 uptime is 24 hours a day 7 days a week
AMEX a stock exchange in New York
12th coming next after the eleventh and just before the thirteenth in position
20th coming next after the nineteenth in position
AARP an association of people to promote the welfare of senior citizens
70th the ordinal number of seventy in counting order
ARDS acute lung injury characterized by coughing and rales
30th coming next after the twenty-ninth in position