A trackball is a ball sitting in a holder that you roll with your fingers or your palm to move the pointer on a computer screen. Think of a mouse turned upside down: with a mouse you push the whole thing around the desk, but with a trackball the body stays still and only the ball turns.

A trackball一個軌跡球is是a ball一顆球sitting in a holder放在一個座子裡的that you roll你用手指轉動的with your fingers or your palm用手指或手掌to move the pointer來移動指標on a computer screen在電腦螢幕上的。Think of把它想成a mouse turned upside down一隻翻過來的滑鼠：with a mouse用滑鼠時you push你是推whole thing整個東西around the desk在桌上移動, but但with a trackball用軌跡球時the body外殼stays still不動and而only the ball只有球turns在轉。

Because your arm does not move, some people use one when their wrist or shoulder hurts from using a mouse, and it is handy where there is no desk space at all. Trackballs were common on early laptops and are still used in air traffic control, in some medical machines, and by people who simply prefer them, but for most people today the mouse and the touchpad have taken over.

Because因為your arm你的手臂does not move不用動, some people有些人use one會用它when their wrist or shoulder hurts當他們的手腕或肩膀from using a mouse因為用滑鼠而痛的時候, and而且it它is handy很方便where there is no desk space at all在完全沒有桌面空間的地方。Trackballs軌跡球were common以前很常見on early laptops在早期的筆電上and和are still used現在仍用於in air traffic control航空管制, in some medical machines一些醫療機器裡, and和by people用它的人who simply prefer them只是單純比較喜歡它, but不過for most people today對現在大多數人來說the mouse and the touchpad滑鼠和觸控板have taken over已經取代了它。

So it is a real, current word — just not an everyday one.

So所以it它is是a real, current word一個真實、現在仍在用的字——just不過not an everyday one不是天天會用到的字。