1. Aphasia - impaired speech and language perception
2. Apnea - cessation of breathing
3. Appendicitis - inflammation of the appendix; removal of the appendix is an appendectomy
4. Arthritis - inflammation of a joint
5. Asthma - difficulty breathing because air cannot be efficiently expelled
6. Astigmatism - loss of image sharpness that causes eyes to tire easily
7. Ataxia - walking problems result from the lack of muscle coordination
8. Atrophy - wasting away of muscle or organ
9. Audiogram - hearing test
10. Aura - often precedes a migraine, headache, or seizure
11. Avascular Necrosis (osteonecrosis) - bone death
12. Achondroplasia (formerly called dwarfism)
13. Adenoiditis - inflammation of the adenoids, which are in the throat and help prevent infection
14. Allergy - antigens cause a hypersensitive body immune response
15. Amputation - loss of an extremity that usually necessitates a prosthesis
16. Anemia - low red blood cell count results in fatigue and shortness of breath
17. Aneurysm - dilation of blood vessel that could result in rupture
18. Angiogram - X-ray of blood vessels
19. Angioplasty - coronary artery is enlarged by a balloon-tipped catheter
20. Ankylosing spondylitis - inflammatory disease of joints and ligaments
21. Anoxia - lack of oxygen
22. Antibiotics - drugs that fight bacterial infection