As a noun:
* I took the train to work this morning.
* The train was delayed due to bad weather.
* The train tracks were covered in snow.
As a verb:
* I'm going to train for a marathon.
* The company trains its employees in customer service.
* The dog is being trained to sit and stay.
Other uses:
* The train of thought led me to a surprising conclusion.
* The wedding train was beautiful.
* The train of cars stretched for miles.
The specific meaning of "train" will depend on the context of the sentence.