WordNet sense 1 (coil forming the part of an electrical circuit such that changing current in it induces a current in a neighboring circuit):

primary coil, primary winding

WordNet sense 2 (one of the main flight feathers projecting along the outer edge of a bird's wing):

primary feather, primary quill

WordNet sense 3 (of or being the essential or basic part):

elemental, elementary

WordNet sense 4 ((of e.g. information) not secondhand or by way of something intermediary):

original

WordNet sense 5 (being an immediate result or consequence):

direct

WordNet sense 6 (most important element):

chief, main, principal

WordNet sense 7 (of great significance or value):

of import

WordNet sense 8 (of primary importance):

basal

WordNet sense 9 (basic and fundamental):

essential

WordNet sense 10 (not derived; primary or simple):

underived

WordNet sense 11 (a preliminary election where delegates or nominees are chosen):

primary election