1.  headache(n = noun.cognition) concern, vexation, worry - something or someone that causes anxiety; a source of unhappiness; "New York traffic is a constant concern"; "it's a major worry"
is a kind of negative stimulus
has particulars: bugaboo, burden, encumbrance, incumbrance, load, onus, business

2.  headache(n = noun.state) cephalalgia, head ache - pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs;
is a kind of ache, aching
has particulars: cluster headache, histamine headache, hemicrania, megrim, migraine, sick headache, sick headache, sinus headache, tension headache

   Pain in the head; cephalalgia. Macaulay. [1913 Webster]

headache, n.
1 a continuous pain in the head.
2 colloq. a a worrying problem. b a troublesome person.

Derivative:
headachy adj.

N  physical pain, pain, suffering, sufferance, suffrance, bodily pain, physical pain, bodily suffering, physical suffering, body pain, mental suffering, dolour, ache, aching, smart, shoot, shooting, twinge, twitch, gripe, headache, stomach ache, heartburn, angina, angina pectoris, hurt, cut, sore, soreness, discomfort, malaise, cephalalgia, earache, gout, ischiagra, lumbago, neuralgia, odontalgia, otalgia, podagra, rheumatism, sciatica, tic douloureux, toothache, tormina, torticollis, spasm, cramp, nightmare, ephialtes, crick, stitch, thrill, convulsion, throe, throb, pang, colic, kink, sharp pain, piercing pain, throbbing pain, shooting pain, sting, gnawing pain, burning pain, excruciating pain, anguish, agony, torment, torture, rack, cruciation, crucifixion, martyrdom, toad under a harrow, vivisection, in pain, in a state of pain, pained, gouty, podagric, torminous, painful, aching, sore, raw, Special Sensation (1) Touch.

cluster headache, headache powder, histamine headache, sick headache, sinus headache, tension headache