As well as spelling, there are some big differences in how whisky/whiskey is produced in Scotland and Ireland.
Single Malt Scotch has to be made from malted barley. The spirit is distilled in a copper pot still and has to be aged for a minimum of three years in an oak cask.
On the other hand, Blended Scotch is made from a mix of single malts and so-called grain whisky, which is made from grain and is produced in a column still. It also has to be aged in an oak cask.
The oldest type of Irish whiskey is Single malt, which is made from malted barley in a copper pot still. But there are also a number of other different styles, including Single Pot Still, which is made from both malted and unmalted barley.
This was done because traditionally distillers were taxed on how much-malted barley they used. There are many legendary brands in this category, including Method & Madness, Green Spot, and Redbreast.
Many of the largest Irish whiskey brands are blends, like Jameson and Bushmills White Label, which are made from a mix of grain whiskey and pot still or malt whiskey.