---- > [!definition] Definition. ([[periodic]]) > Let $A$ and $B$ be sets, where addition makes sense in $A$. A function $f: A \to B$ is called **periodic** provided that there exists $x_{0} \in A$ such that for all $x \in A$ we have $f(x+x_{0})=f(x).$ A function that is not **periodic** is called **aperiodic**. ---- #### ---- #### References > [!backlink] > ```dataview > TABLE rows.file.link as "Further Reading" > FROM [[]] > FLATTEN file.tags as Tag > WHERE Tag = "#definition" OR Tag = "#theorem" OR Tag = "#MOC" OR Tag = "#proposition" OR Tag = "#axiom" > GROUP BY Tag > ``` > [!frontlink] > ```dataview > TABLE rows.file.link as "Further Reading" > FROM outgoing([[]]) > FLATTEN file.tags as Tag > WHERE Tag = "#definition" OR Tag = "#theorem" OR Tag = "#MOC" OR Tag = "#proposition" OR Tag = "#axiom" > GROUP BY Tag > ```