What is "primaries"

Primary \Pri"ma*ry\, n.; pl. Primaries.

1. That which stands first in order, rank, or importance; a chief matter.

2. A primary meeting; a caucus.

3. (Zo["o]l.) One of the large feathers on the distal joint of a bird's wing. See Plumage, and Illust. of Bird.

4. (Astron.) A primary planet; the brighter component of a double star. See under Planet.

n. (plural of primary English)