The meaning of "mixture"

Memorable words of claim construction:

Thus, it appears the court construed
“mixture” to mean “a mixture.” We agree that “mixture”
does not require any additional construction.

Of comprising:

We note,
however, that the phrase construed by the trial court is
actually “a mixture comprising” various ingredients.
While the claimed mixture must include the listed ingre-
dients, it is not limited to them, and may optionally
include other components in addition to those explicitly
recited. CIAS, 504 F.3d at 1360-61.