• 測定そくてい — measurement / gauging
• 観測かんそく — observation
• 推測すいそく — speculation / guess
• 予測よそく — prediction / forecast
• 実測じっそく — actual measurement
• 不測ふそく — unforeseen / unexpected

測 is made up of the radical 氵 (water) and the phonetic element 則 (ソク). Since measuring depth was often done in water, the radical reflects the origin of the meaning. The character carries the broader idea of “measurement” — physical or abstract.

川の深ふかさを 測はかる。
Measure the depth of the river.

気温きおんを 測はかってください。
Please take the temperature.