See The Modal Assurance Criterion – Twenty Years of Use and Abuse [pdf]

Modal Assurance Criterion
Coordinate modal assurance criterion (COMAC)
Frequency response assurance criterion (FRAC)
Coordinate orthogonality check (CORTHOG)
Frequency scaled modal assurance criterion (FMAC)
Partial modal assurance criterion (PMAC)
Scaled modal assurance criterion (SMAC)
Modal assurance criterion using reciprocal modal vectors (MACRV)