無常 is the Buddhist teaching that nothing holds its form: all that arises changes and passes. 無 is without and 常 is constant, always the same, so the word says simply not constant. It is a truth about the world, not a feeling of doubt. In Japanese it can also mean a death, and its poems give it a feeling English has no single word for. Whether you take it as a comfort or as a reminder to treasure what is here now is yours.
無常 is composed of the kanji 無 (read mu) meaning "without, not" and 常 (read jō) meaning "constant, unchanging".
The word is older than Buddhism, meaning without constancy in the 易 and the 孫子, and the translators of the sutras took it for the Sanskrit anitya, the impermanence of everything that arises, which is the sense it carried into Japan, where a poet of 750 already reads it as 常なし.
We want you to be as happy with the meaning as you are with Master Takase's art. To learn more, visit Philology of 無常.