Ah yes, picking nits.. well, a 2x4 actually measures 1.5 x 3.5 according to my tape measure. Still, that's a pretty fur piece from a parsec. ;)
But your point is valid. I agree that 2 x 4 is 2 BY 4 and represents a unit of measure while 16:9 is an aspect ratio. Although I prefer 16 TO 9 I have...
>Isn't a parsec a measurement of time?<
Actually, a parsec is a distance measurement.
Merriam-Webster defines it as:
"a unit of measure for interstellar space equal to the distance to an object having a parallax of one second or to 3.26 light-years"
Han Solo sorta misspoke there, methinks...