> [!definition] > > Let two binary [[Code|codewords]] $a$ and $b$ have equal length. The *Hamming distance* $d(a, b)$ between them is the number of symbols in $a$ which are different from $b$. > > Hamming distance may be used as a [[Decision Rule|decision rule]], where the codeword with the **minimum** distance to the one received will be selected.