Tara is right. They mean basically the same thing. "Aware" is always fine to use. I only use " cognizant" in situations where I'm trying to be academic with my words or really emphasize my awareness by using more academic language.

They are often used interchangeably. "Cognizant" is usually used in reference to knowledge. For example: (a) "The school is cognizant of the needs of the students"; (b) "Politicians must be cognizant of their responsibilities". "Awareness" can be used in reference to knowledge but also to stimuli. For example: (a) "I am aware of those facts"; (b) "He was aware of the dog"; (c) They were aware of the risks". "Cognizant" is used less often and is more formal. It is usually reserved for academic contexts. A synonym for it would be "mindful". A synonym for "aware" would be closer to "know of" or "alert".

Both mean the same thing. Cognizant= scientific, academic usage. Aware= casual usage.

They mean the same thing, but cognizant is a less common word. English has many synonyms. Most are used in everyday speaking, but some, like cognizant, are usually reserved for more academic settings. Amusingly, the more academic words, because they come from Latin, often through French, are more familiar for learners whose first languages are French, Spanish, or Portuguese.