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Monitor
noun
1.
an instrument or device used for observing, checking, or keeping a continuous record of a process or quantity.
"a heart monitor"
Similar:
detector
scanner
recorder
security system
security camera
CCTV
2.
a television receiver used in a studio to select or verify the picture being broadcast from a particular camera.
verb
observe and check the progress or quality of (something) over a period of time; keep under systematic review.
"equipment was installed to monitor air quality"
Similar:
observe
watch
keep an eye on
keep track of
track
keep under observation