In retail environments within the fields of construction, manufacturing, and engineering, the terms lineal and linear often get interchanged without any loss of meaning. However, engineers know the difference.
Lineal describes a quantity of material that has an implied width dimension, and
linear describes a distance irregardless of width. As such, OEM manufacturers, tier 1 distributors, and engineers specify
lineal units almost exclusively (the distinction has begun to erode recently), while anyone taking a length measurement is observing a
linear unit. Consider the following example: "We need to replace a single metal panel, and the building's sidewall is 12
linear feet to the eave, so we will need to order 12
lineal feet of metal. " Furthermore, while there is always a conversion factor to convert
lineal feet to square feet (defined by the width of the material specified), such a concept does not properly apply to measurements that use the term
linear (despite the fact that online converters for the retail market are widely distributed on the internet). Reference for all uses of
linear:
http://www.merriam-webster.com/dictionary/linear Reference for Lineal as referring to matters of ancestry or lineage:
http://www.merriam-webster.com/dictionary/lineal OEM and value added commodity manufacturers, tier 1 distributors, and engineers generally do not market directly to consumers, therefore there is no readily available reference that I know of that describes the specific meaning of lineal as it is used in industry. I may only submit the above based on my own 20 years experience in using both terms daily.