Merge: A group to which fiber production is assigned based on properties and dyeability. All fibers within a merge can be expected to behave uniformly, and for this reason, can be mixed or used interchangeably.

Metric Count: The number of kilometers per kilogram of yarn.

Modulus: The ratio of change in stress to change in strain following the removal of crimp from the material being tested; i.e., the ratio of the stress expressed either in force per unit linear density or force per unit area of the original specimen, and the strain expressed either as a fraction of the original length or as percentage elongation.

Moisture Regain: The percentage of moisture in a textile material brought into equilibrium with a standard atmosphere after partial drying, calculated as a percentage of the moisture-free weight.

Monofilament: Any single filament of a man-made fiber, usually of a denier higher than 15. Instead of a group of filaments being extruded through a spinner to form a yarn, monofilaments may be used for textile uses such as hosiery or for nontextile uses such as bristles.