Various<unk> es with nomenclature. Not every<unk>  contains a Q wave, an R wave, and an S wave. By convention, any combination of these waves can be referred to as a<unk> . However, correct interpretation of difficult ECGs requires exact labeling of the various waves. Some authors use lowercase and capital letters, depending on the relative size of each wave. For example, an<unk>  would be positively deflected, while an<unk>  would be negatively deflected. If both<unk> es were labeled RS, it would be impossible to appreciate this distinction without viewing the actual ECG. Monomorphic or polymorphic Monomorphic refers to all<unk>  waves in a single lead being similar in shape. Polymorphic means that the<unk>  change from<unk>  to<unk> . These terms are used in the description of ventricular tachycardia.
QRS complex
J wave
U wave
P wave 
Delta wave
T wave
ST segment
Plateau potentials