Realize and recognize are close in meaning, but they are not interchangeable.
Realize means to become aware of something, often suddenly. It describes a moment of understanding. For example, I realized I had left my phone at home. The focus is on new awareness.
Recognize means to identify someone or something because it is already known to you. For example, She recognized him from college. The focus is on knowing what or who it is.
- Use realize for new understanding.
- Use recognize for identification.
A quick contrast helps: I realized the answer was wrong means I suddenly understood it. I recognized the answer from yesterday’s lesson means I had seen it before and knew it.
If you mean become aware, choose realize. If you mean identify from memory or familiarity, choose recognize.