These are two words with rhyming pronunciations but that is where the similarity ends. A delusion is a wrong belief regarded as from the point of view of the person holding it( and has special uses in psychiatry, as in delusions of grandeur). For example: She has always had the delusion that she is a great singer. An illusion is also an impression that something not true or real is true or real, but it is usually a fleeting impression, something that is regarded externally. For example: Optical illusions make things appear to be other than they really are, in the world as we know it, freedom is largely an illusion.

Illusions are the works of magicians, they create visual tricks, like making themselves disappear and making a pigeon appear instead. Our eyes can be fooled by these optical illusions.

Delusions are meaner than illusions. Delusions refer to a belief in something is false. The most common usage of delusions is the phrase ‘delusions of grandeur’, and if we let delusions run their own course, we can wind up at the psychiatrist’s office; this is how potent delusions can be. So you better be careful and don’t allow yourself to be deluded by the illusions and conjuring tricks of the world.

Tool tip to remember the difference :

Just Remember: The i in ‘illusion’ stands for ‘illusory’, the d in ‘delusion’ stands for ‘deluge of false beliefs’.

Examples of incorrect uses of delusion and illusion:

1. The act was part denial and part illusion.
2. Advertisements are shown to maintain the delusion of reality.

Examples of correct uses of delusion and illusion:

1. What he witnessed was just a delusion of reality.
2. He created an illusion that had the appearance of the truth.
3. We have no illusion that these credits are going to create lots of new job. (New York Times)
4. “Basically, I think he’s suffering from delusions of grandeur,” he said. (Chicago Tribune)

A Quick Recap:

These two can cause some delusions and illusions.

A delusion is a wrong belief regarded as from the point of view of the person holding it( and has special uses in psychiatry, as in delusions of grandeur). For example: She has always had the delusion that she is a great singer.

An illusion is also an impression that something not true or real is true or real, but it is usually a fleeting impression, something that is regarded externally. For example: Optical illusions make things appear to be other than they really are, In the world as we know it, freedom is largely an illusion.