Corus steelworks at Redcar next to the River Tees
The dictionary definition of mothballing is 'The preservation of a production facility without using it to produce.'
Machinery should be kept in working order so that production can be restarted.
Christos Tsinopoulos is a Lecturer in Operations Management at Durham University:
'Some plants do this due to lack of investment and orders, or when other plants are more suitable.'
Christos thinks that Corus could re-open after mothballing, but only if the timing is right:
"If it were to open immediately and the plant got large orders, it could be back to full working order if given time and some investment.
"In this situation it's likely that some equipment will be sold as this will be what competitors want to buy.
"It will also be difficult to re-open the plant if the people who work there, who have specialist knowledge and skills, move onto other jobs somewhere else.
"Their expertise will start being placed in other parts of the economy.
Kirby Adams - the Europe chief of Tata Steel, which owns Corus
"(This partial mothballing) is temporary but if you lose key people it will be difficult to re-start the plant.
"As this closure will have a large local impact it should get Government support, which of course would ensure it starts up again quickly."
Kirby Adams, the Europe chief of Tata Steel which owns Corus, said that Corus had funded the business since May, and at one point, it looked very likely that the plant would close in August:
"Corus is not in a position where it can bankroll a loss-making business such as Teesside," Mr Adams said in a press conference.
"We are acutely aware that this will be devastating news for our employees, our contractors and their families,".