In Unix/Linux terminology, are the words 'device' and 'drive' synonymous?
No. Drives are devices, but not all devices are drives.
The Wikipedia article on device files lists a number of non-drive devices. For example, audio hardware is a device. Serial & parallel ports are devices. USB-connected gadgets are devices.
Keep in mind that some devices that are not drives may identify as such, a noteworthy example is most Android devices that identify as a drive but use a mechanism other than a drive unless it is mounted as USB storage.