Technically, the phrase Electric Toothbrush covers the Ultrasonic Toothbrush entity too. But, as both Electric Toothbrush and Ultrasonic Toothbrush are consumer grade products, they are different entity and the products are named accordingly indicating the technology working behind.
The size and mass of a Done depends on the desired operational capabilities – few grams to several tons. The autopilot system or control from the ground opens a new opportunities for very long flights of several tens of hours.
WordPress is basically a blogging platform written in PHP which uses MySQL database. When WordPress was first written, the target was never in mind to make it a highly scalable platform – frankly, there was no resource. MySQL, possibly the most used database with PHP combination has certain issues – itself it is not great for performance.