Richard–Berry paradoxA paradox highlighting an issue with using description length as a measure of complexity.
Define a specific natural number as "the least natural number that cannot be described in fewer than 20 words".
If such a number does exist, then we have just described it in 13 words, contradicting its definition. If such a number doesn't exist, then all natural numbers can be described in fewer than 20 words.
Thus, there is a need for the meaning of 'description' to be inspected closely.
SourceM. Li and P. Vitányi, An Introduction to Kolmogorov Complexity and ItsApplications.