The word for ‘special’ in French is spécial.
In use, you might say, for example, un événement spécial, which means ‘a special event.’ The pronunciation can be a bit tricky, so it’s helpful to listen to native speakers or use a language app to get it right. Just remember that in French, adjectives often agree in gender and number with the nouns they describe. So if you’re talking about a ‘special’ feminine noun, like ‘occasion,’ you would use spéciale.