Q: Commonly used as a symbol for flow rate (quantity). Units may be expressed as any volume per unit time.
Quadrant: Referring to 1/4th of the circumference of a circle, spanning 90°.
Quadratic: A polynomial equation where the unknown is raised to the power of 2. For example: 9x2+3x+1 =4.
Quality control: A business process to verify and maintain a desired standard of quality in a product or production system.
Quench: Adding fluid outside the seal to either cool the seal, or to dilute any product leaking out of the seal face.
Quill shaft: A shaft that is hollow, containing another shaft inside of it.