extension field

Extension field

If ${\displaystyle K}$ is a subfield of ${\displaystyle L}$, then ${\displaystyle L}$ is an extension field or simply extension of ${\displaystyle K}$, and this pair of fields is a field extension. Such a field extension is denoted ${\displaystyle L/K}$ (read as "${\displaystyle L}$ over ${\displaystyle K}$").