English has quite a few words that are spelled two ways and mean the same thing. When you look these words up in the dictionary, the convention is to give the preferred spelling first. Here are some words you can spell two ways:
British people write judgement, while in America we omit that middle e. Similarly, they write colour, honour, centre and theatre, while Americans prefer color, honor, center and theater. Language changes in spelling, grammar, meaning and usage, but the changes are rarely so rapid that you can’t keep up.