A number field of degree n is an old field if it is contained in the compositum of fields, each with degree strictly less than n. A field which is not old, is new.
Note that fields of prime degree are always new, so this discussion only applies to the tables displayed here for degrees 4 and 6.
In general, we flag new fields by displaying their Galois groups in boldface. When the number of fields becomes particularly large, we separate old fields from new fields.