Ramification in a finite extension 
of local fields is measured
by its ramification index 
. If 
and 
are the maximal ideals
in the corresponding valuation rings, then 
is defined by
 |
The extension is ramified if 
and unramified if 
. If the residue characteristic
divides 
,
the ramification is wild ramification; otherwise
it is tame ramification.
