Realize
Part of speech: verb
Definition: To become aware of a fact or situation. To make real; to convert from the imaginary or fictitious into the actual; to bring into concrete existence; to accomplish. To cause to seem real; to impress upon the mind as actual; to feel vividly or strongly; to make one's own in apprehension or experience. To convert (assets) into actual money. To convert into real property; to make real estate of. To acquire as an actual possession; to obtain as the result of plans and efforts; to gain; to get; as, to realize large profits from a speculation. To convert any kind of property into money, especially property representing investments, as shares, bonds, etc.
Example sentence: All the adversity I've had in my life, all my troubles and obstacles, have strengthened me... You may not realize it when it happens, but a kick in the teeth may be the best thing in the world for you.
Realise
Part of speech: verb
Definition: To make real; to convert from the imaginary or fictitious into reality; to bring into real existence
Example sentence: Even if I stumble on to the absolute truth of any aspect of the universe, I will not realise my luck and instead will spend my life trying to find flaws in this understanding - such is the role of a scientist.