Weight
In modern scientific usage, weight and mass are fundamentally different quantities: mass is an intrinsic property of matter, whereas weight is a "force" that results from the action of gravity on matter: it measures how strongly the force of gravity pulls on that matter. However, in most practical everyday situations the word "weight" is used when, strictly, "mass" is meant. For example, most people would say that an object "weighs one kilogram", even though the kilogram is a unit of mass.
Mass spectrometry
There are several important analyser characteristics. The mass resolving power is the measure of the ability to distinguish two peaks of slightly different "m/z". The mass accuracy is the ratio of the "m/z" measurement error to the true m/z. Mass accuracy is usually measured in ppm or milli mass units. The mass range is the range of "m/z" amenable to analysis by a given analyzer. The linear dynamic range is the range over which ion signal is linear with analyte concentration. Speed refers to the time frame of the experiment and ultimately is used to determine the number of spectra per unit time that can be generated.