am - ante meridiem (before midday)
HR - Human resources
Q&A - Question and Answer
ADHD - Attention deficit hyperactivity disorder
SAD - Seasonal affective disorder
pm - post meridiem (after midday)
MAD - Mutually Assured Destruction
ME - Myalgic encephalomyelitis
PTSD - Post-traumatic stress disorder
R&R - Rest and Recuperation
Q.E.D. - quod erat demonstrandum (which is what had to be proven)