6.NS.6b says:

Understand signs of numbers in ordered pairs as indicating

locations in quadrants of the coordinate plane; recognize that

when two ordered pairs differ only by signs, the locations of the

points are related by **reflections** across one or both axes.

The next time we see reflections in 8th grade geometry, where, it is introduced. Is it expected that students talk about, say, (1, 0) and (-1, 0) in terms of a reflection across the y-axis or is the reference to reflections addresses the underlying mathematical structure but not how students will be talking about this situation (similar to them using commutativity in 1st grade but not using the term)? I guess, given that students should be familiar with the idea of symmetry from at least grade 4, there is a familiar language that students can use.