radioisotope; radioactive isotope
course; route; path; process; stages
may; might; perhaps; may be; possibly
in case of; at that time; at this time
separation; isolation; extrication; release; isolation
flow (of a fluid or gas); stream; flow (of people, things); passage (of time); course (of events); (step-by-step) procedure; group of people who remain together after the end of an event
(heavy) drinker; drunkard; tippler; boozer
weak; frail; delicate; tender; unskilled; weak (wine)
measure; step; dealing with; medical treatment
Second World War (1939-1945); World War II; WWII; WW2
German Air Force; Luftwaffe
allied forces; the Allies (e.g. in WWII)
postwar period; period after Second World War
source of protein; protein source
culture medium; growth medium
infiltration; permeation; exudation; percolation; effusion; extraction
sulfurous acid; sulphurous acid
riddle; puzzle; enigma; enigmatic; mysterious
abrupt; sudden; unexpected
free (of restraint, controls, etc.); free (of charge); freelance; independent; freelancer; one-size-fits-all; free skating
sale; sales; selling; marketing
interruption; discontinuance; suspension; cancellation (of a planned event); calling off
to be at a loss; to be puzzled
personal history; background; career
to abandon; to fail; to desert; to forsake
migration; move; emigration; immigration
mundane; routine; everyday; unremarkable; common; day-to-day
soil; breeding ground (for); fertile ground (for)
clue; lead; key; handhold; hold