Adjective
(mathematics, logic) Of one of a series of models, languages, relationship, forms of logical discourse, etc., being the simplest one or the first in a sequence.
Of fundamental importance.
Source: en.wiktionary.orgfirst order
Of course, I love tools. I also love arranging them, to the point where I came up with a name for my organizing metric: first-order retrievability. Adam Savage
Call it habit or conditioning or socialization: The citizens of the United States have essentially forfeited any capacity to ask first-order questions about the fundamentals of national security policy. Andrew Bacevich
A3D uses a subset of the actual in-game 3D world data to accurately model the location of both direct (A3Dspace) and reflected (A3Dverb) sound streams (A3D 2.0 can perform up to 60 first-order reflections). Source: Internet
Alphabet Unlike natural languages, such as English, the language of first-order logic is completely formal, so that it can be mechanically determined whether a given expression is legal. Source: Internet
A first order lens has the longest focal length, with the sixth being the shortest. Source: Internet
A first-order emergent structure occurs as a result of shape interactions (for example, hydrogen bonds in water molecules lead to surface tension ). Source: Internet