幻觉 (huànjué): This is the most common and general word for illusion, referring to a false perception or a distorted view of reality.
错觉 (cuòjué): This refers to an optical illusion or a misperception of something due to a physical or psychological factor.
假象 (jiǎxiàng): This refers to a false appearance or a deceptive impression.
幻影 (huànyǐng): This refers to a phantom or an apparition, often used in the context of a ghost or a spirit.
魔术 (móshù): This literally means "magic," but it can also refer to illusions performed by a magician.
The best choice for the word "illusion" depends on the specific context. For example, if you are talking about a visual illusion, 错觉 (cuòjué) would be the most appropriate word. If you are talking about a general sense of delusion or a distorted perception of reality, 幻觉 (huànjué) would be the best choice.