focus

In Canadian usage, the verb focus may be spelled with a single or double s before a suffix.

• As a forensic scientist, Rosalind focuses (or focusses) on minute details.
• The speaker was having trouble focusing (or focussing) his thoughts during the noisy demonstration.
• Barbara Cass-Beggs focused (or focussed) on the musical abilities of young children.

The correct phrasal verb is focus on, and not the logically unsound focus around.

• The RCMP investigation focused on (not around) the misuse of public funds.

The plural of the noun is focuses or foci (generally encountered in the sciences).

• The political campaign organizers identified three potential focuses before the election.
• A circle has one central point, but an ellipse has two foci.