Forty.
Decipher is how it is spelled in British English.
In England we spell it Realised, with an S not a Z.
You spell it like this, tyre, for plural, it's tyres.
Behaviour is the correct British English spelling.
The number is spelled "forty" everywhere in English.
The UK and US spellings are both wonderful. This is not a word that has variant spellings.
The US spelling is organized. The UK spelling is organised.
The correct spelling is "mesmerised" (UK English) or "mesmerized" (US English).
Endeavour is the British English spelling which is used in the UK.The US English spelling is endeavor.
The spelling is the same as the US: alleviate (reduce a problem)
Analyze is the correct English spelling, though Brits may spell it as analyse.
A century, meaning 100 years or 100 runs in cricket is the correct English spelling.