Having one's attention concentrated on a particular activity or purpose. Alternative spelling of 'focused' primarily used in British English.
From Latin 'focus' meaning hearth or fireplace, the central point where fire burns. The metaphorical sense of concentration developed in the 17th century, with the past participle form emerging later.
The double 's' in 'focussed' reflects British spelling conventions, much like 'organised' vs 'organized'. Interestingly, the original Latin 'focus' meant the central hearth of a Roman home, making concentration literally about gathering around the fire of attention.
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