It's a common root in many English words, often indicating the action of throwing or projecting something:
* Inject: to throw something into (like medicine)
* Eject: to throw something out
* Project: to throw forward (like a plan)
* Projectile: something thrown forward (like a bullet)
So, while "ject" doesn't directly translate to a single English word, it captures the sense of throwing, projecting, or pushing forward.