Recognize means to remember, acknowledge truth or legal authority, or to realize something.
British English lists an alternate spelling as recognise, but the main entry is recognize. North Americans (yes, that includes Canada) prefer the ize spelling, and this is accepted everywhere. However, outside North America some prefer the ise spelling and it is not incorrect. This spelling change goes across all derivatives including: recognizability, recognisability, recognizable, recognisable, recognizeably, recognisably, recognizer, and recogniser.
The ize/ise change is based in English being influenced by French, and every other language. The Greek words changed to Latin, which used a z, but the French spelled it with an s. Purists in England promote the original ize while others stick with convention, ise.
Examples
But on April 15, the European Parliament joined Vatican City and 22 other nations in recognizing the Armenian genocide and called upon Turkey to do the same. [The Boston Globe]
“We had some really strong performances last year (at the galas), but maybe the recognizability factor (of the hosts) wasn’t as strong.” [Winnipeg Free Press]
When the UN General Assembly voted to recognise the newly born Jewish state on November 29, 1947, Greece abstained. [The Jewish Chronicle Online]
The update adds features such as hands-free actions, always-on apps, WiFi support and an emoji recogniser, all of which will help Android Wear devices like the LG Watch Urbane and Moto 360 compete with the Apple Watch. [The Telegraph]
Tipping the scales at almost half a stone, it is a weighty book, literally and figuratively, and one that provides valuable illumination on the question of what exactly it is that makes a garden recognisably Irish. [The Irish Times]