# 'Length measure' vs. 'length measurement'

I have to write a scientific paper where I refer to a CAD drawing. Now, I'm a bit confused, because I have to refer to the length "parameters" on that drawing (as opposed to the angle "parameters"), e.g. the segment lengths l1, l2, ... Should I refer to these length parameters as "length measurements" or as "length measures"? I used both as a synonym so far, but I'm not sure if that is accurate.

To me, a measurement is a reading of a quantity. In your situation it is length, for an electrical engineer it might be volts or amps.

Likewise, my interpretation of a measure is an action undertaken, such as: "the air strike in Foobar province was a measure against counter insurgency".

For your paper, I would suggest you use length measurements.

• There are a great deal of other ways to interpret "measure" as a noun but I agree that a measurement is a observation or reading. In this case we seem to be dealing with nominal values, not having actually been measured, and for that reason I think the suggestions in other answers of using the term "dimension" are more on point (regardless of whether it's indicated as an option in the original statement). – Air Feb 19 '16 at 22:58

The usual practice is to refer to measurements on a drawing as 'dimensions'.

For example you might say 'dimensions L1, L2 and L3 are determined by calculation'.

The term dimensions also implies that you are talking about nominal values whereas 'measurements' implies real world data. The difference between dimensions and measurements is defined by tolerances.

If there is a particular need to be unambiguous you can talk about linear, radial, angular or diametric dimensions. But dimension is the generic terms for any measurement on a drawing. In most cases this will be entirely clear from the units used.

It is also best to be careful using terms like 'length' generically as they can be misleading. For example the diameter of a hole is a linear dimension but it is not a length. Length implies that you are referring on a straight line on the drawing as opposed to say, the distance between two parallel lines.

The general terminology is :

• Length : distance between two points forming a straight line
• Radius : used for incomplete circular arcs eg fillets or bends
• Diameter : used for complete circles eg holes and shafts

In CAD the term 'parameters' is often used to refer specifically to dimension values in a model which are variable and assigned values from some external table, formula, function etc. Parametric values will also often be related to one another eg L2 is defined as being half L1. For example you might design a generic part which is produced in several variations so you can produce a drawing for each version simply by referencing a table of dimensions rather than manually redimensioning the model for every version required.

The conventional term would be a linear dimension if you just want to specify that your measurement is of a length. There are also angular dimensions for angles, and more complicated dimensional features like tolerances.

If you're discussing the CAD drawing in terms of the CAD program (not just to describe the object it shows) and you want to identify your parameters you would want to distinguish between a driving dimension and a driven dimension. A driving dimension is a length, angle or other number that you enter which is driving your model. A driven dimension is a length that you are showing in your drawing, but which is automatically determined based on the driving dimensions you provide.

It's worth noting that specific CAD packages have more complicated names to describe how a dimension is created (eg. Autocad distinguishes between linear and aligned dimensions to describe how it sets the axis of the dimension) but in the context of the final drawing, most dimensions still fit into these two categories.