aboard — abroad
“Aboard” means ‘on or onto, in or into a bus, train, aeroplane or ship’,
All passengers went aboard the train.
In the plane crash, all the passengers aboard were killed.
“Abroad” means ‘in a wide area; everywhere; outside one’s own country’’
Our teacher had his education abroad.
My son wants to go to abroad for higher studies. [wrong]
My son wants to go abroad for higher studies. [right]
She had her training in abroad. [wrong]
She had her training abroad. [right]
They are coming back home from abroad. [right]