abstract
alarm
alert
background
blue
concept
crisis
culmination
curve
danger
earthquake
flood
fluctuation
forecast
frame
frequency
glowing
graphic
hazard
laboratory
line
magnitude
medical
medicine
menace
observation
oscillations
oscilloscope
outlook
paper
peak
pen
placard
poster
red
research
risk
science
scientific
sign
stress
symbol
threat
tsunami
unrest
wallpaper
warning
watch
wave