Attention deficit hyperactivity disorder (ADHD) should be diagnosed and treated in children as young as age 4, according to new guidelines from the American Academy of Pediatrics. Skip to main content
ephemeris. 1  a table showing the positions of a heavenly body on a number of dates in a regular sequence. 2  an astronomical almanac containing such tables. 3  Archaic. an almanac or calendar.
ephemeris time; TDT; terrestrial dynamical time; terrestrial time; TT. Hypernyms (TT is a kind of...): time unit; unit of time (a unit for measuring time periods) Domain category: astronomy; uranology (the branch of physics that studies celestial bodies and the universe as a whole)