Make sure that you know which system of spelling you are using. You are free to use whichever system you are accustomed to, but be consistent throughout your writing.
United States | United Kingdom | Canada |
color, favorite | colour, favourite | colour, favourite |
center, meter | centre, metre | centre, metre |
organize, analyze | organise, analyse | organize, analyze |
organization | organisation | organization |
traveling, traveled | travelling, travelled | travelling, travelled |
learned, dreamed | learnt, dreamt | learned, dreamed |
defense, license (n.) | defence, licence (n.) | defence, licence (n.) |
maneuver | manoeuvre | manoeuvre |
gray | grey | grey |