The letter R.
This will be a very important letter in the coming days, weeks, possibly months and years (or maybe forever). Already quite important due to it appearing in many words, the letter R will gain a new significance in the media and with "guided by the science" people as it is an epidemiological symbol representing the average rate of contagion for an infectious disease. In Germany, Merkel has already reliably informed her subjects that when R < 1 then can go out. But if R >= 1 they have to go back inside and stay there until R starts behaving itself. She notes that scores of 1.2 or above are right out, as this will stretch the hospitals beyond breaking point. This assumes the hospitals have become more brittle in recent weeks, considering the German health services are acknowledge to have handled the pandemic quite well at a time R was (frankly) taking the piss with a score of 3 or above. But, as always, the science is fluid and subject to abrupt change and instant reversal.