* Graduated: This means the apparatus has markings (graduations) indicating volume or other units at regular intervals. A graduated cylinder, for example, has lines showing various volumes. These markings are a *guide* for approximate measurements. The accuracy of these markings isn't necessarily guaranteed beyond a certain tolerance.
* Calibrated: This means the apparatus has been precisely measured and its accuracy verified against a known standard. A calibrated pipette, for instance, has been checked to ensure it delivers the stated volume within a specified tolerance. Calibration involves more than just adding markings; it ensures the markings accurately reflect the actual volume or measurement. Calibration usually involves a certificate stating its accuracy and traceability to national or international standards.
In short:
* Graduated implies the *presence* of markings.
* Calibrated implies the *accuracy* of those markings (or other measurements).
A piece of apparatus can be graduated but not calibrated (the markings might be approximate), while a calibrated piece of apparatus is necessarily also graduated (it must have markings to show the measured value). But not all graduated apparatus is calibrated.