This chapter introduces the basic concepts of measurement in Physics and the importance of accuracy in experiments. It explains physical quantities, units, SI system of units, least count, errors in measurement, and the use of instruments like Vernier Callipers and Screw Gauge for precise measurements. Students also learn about simple experiments such as measuring time using a simple pendulum and understanding scientific methods of observation and calculation.Key Topics:• Measurement and units• SI system of units• Least count and accuracy• Vernier Callipers• Screw Gauge• Measurement of time and simple pendulum