focussed

Usage notes

 * The spelling focused is much more common in the US but also more common in the UK, Australia and New Zealand.
 * The Oxford English Dictionary describes the spelling focussed as irregular.
 * The spelling focussed is a widely seen UK spelling but focused, (focuses, focusing) is more common in prestige publications.
 * The spelling focussed is nowadays more common in Canada and New Zealand than in the UK.