The distinction between sheet and plate is as equally ambiguous as a number of other terms used to describe steel product forms. Generally speaking, a sheet is a thinner item of metal that has been cut from a continuously rolled coil. As such, it can be less than 1mm, or up to 25mm, in thickness. A plate is a thicker item of metal that has been produced (rolled) as a single item. Thickness can be up to 150mm or more, but also as low as 2mm from certain producers.
Therefore, it’s quite possible that certain thickness items could be produced via either process and described differently, although both are in the hot rolled condition.
Plate metal is typically used in machines, structural sections and larger fabrications, whereas sheet metal is used in producing appliances and enclosures.