We call the extra words that have been added a parenthesis. Parenthesis can also show words that have been added to a sentence as an ‘afterthought’ – something you maybe didn’t intend to ...

Liz Lochhead's poem The Bargain uses parenthesis to describe a character at the Barras market in Glasgow: 'nothing to sell / but three bent forks a torn / calendar (last year's) / and a broken ...