FFF	Fused filament fabrication is a technology of digital additive manufacturing based on the extrusion and layered deposition of melted thermoplastic. From a technological point of view, FFF is the same as FDM®—fused deposition modeling, the only difference being that while the FDM® is a registered trademark and thus applies to Stratasys machines only, FFF is a term coined inside the RepRap community;
PLA	Polylactic Acid, a polymer commonly used in FFF process
UFL	Ultimate fracture load, maximum load observed during mechanical testing;
UFS	Ultimate fracture strength, calculated stress in the sample caused by UFL;
Sublayer	A layer of plastic already deposited by a FFF 3D printer, which acts as a substrate for the layer being deposited at a given moment;
Filament	Plastic in the filament form used as supply in the FFF process;
Thread	Extruded and deposited thread of plastic mimicking the 3D printed part;
Feed rate	The linear printing speed, the speed of the nozzle traveling across the XY plane while extruding and depositing the plastic threads;
Flow rate	The volume of plastic delivered through the nozzle per unit of time;
Extrusion efficiency	The ratio of real to calculated mass of 3D printed object;
Underextrusion	A characteristic defect in the FFF process resulting in a significant drop in thread thickness or in thread interruptions caused by a shortage of flow rate and low extrusion efficiency.