What are some examples of common nouns that invisible?

You're right to think about this! It's tricky because common nouns usually refer to things we can perceive with our senses. However, there are some examples where the *concept* is common and invisible:

* Ideas: Love, justice, freedom, happiness, sadness. These are abstract concepts that don't have a physical form.

* Emotions: Fear, anger, excitement, joy. These are internal states we experience but can't see or touch.

* Forces: Gravity, magnetism, electricity. These are forces that affect the world but are not visible to the naked eye.

* Sounds: Music, silence, noise. These are vibrations in the air we can hear but not see.

* Time: Moments, hours, days, years. We can measure it but can't touch or see it.

It's important to remember that even though these things are invisible, they are real and have a significant impact on our lives.