There are two types of body waves: compressional (P) waves and shear (S) waves. Primary waves (P-waves) travel the fastest, so they arrive at the recording station (seismograph) first. Secondary or shear waves (S-waves) travel slower than P-waves so they arrive second.
Modified frequency modulation (MFM) is an encoding scheme used by PC floppy disk drives and older hard drives.
Multilevel marketing (MLM) is a business structure in which products are marketed directly to consumers by sales representatives (or distributors) whose compensation is based on their own product sales as well as the sales of the distributors whom they recruited to the multilevel marketing company.