The classification of epilepsy is very complex and has its own shortcomings. The four common methods are as follows: (1) Classification by etiology: primary epilepsy and secondary epilepsy. (1) Primary epilepsy: It is a type of epilepsy in which the cause is not yet known. It accounts for 60-70% of all epilepsies. This type of epilepsy has no structural or functional abnormalities in the brain and no systemic disease is found with existing tests such as head CT, MRI, PET-CT, etc. It is also called: true epilepsy, idiopathic epilepsy. With the advancement of examination methods, it is possible to find the cause of some of these epilepsies, so some people also call this type of epilepsy as cryptogenic epilepsy (there is a cause, just limited to the current means to find out); this type of epilepsy has a more obvious hereditary and familial tendency to appear, so this type of epilepsy is also called hereditary epilepsy, familial epilepsy. Secondary epilepsy: This is a type of epilepsy that has a clear cause. It accounts for 30-40% of all epilepsies. It is also known as symptomatic epilepsy and acquired epilepsy. Common causes include congenital abnormalities of brain development, neurocutaneous syndrome, traumatic brain injury, brain tumor, cerebrovascular disease, intracranial infection (parasites, etc.), brain poisoning (alcoholism, drug poisoning, gas poisoning, etc.) and systemic diseases (fever, diabetes, lupus erythematosus, etc.). (2) Classification by clinical seizures and EEG: the commonly referred to seizure classification. There are three categories: ① generalized seizures: such as generalized tonic-clonic seizures (commonly known as grand mal seizures), disoriented seizures (commonly known as petit mal seizures), etc. ② Partial seizures: such as twitching of hands and feet, eyelid twitching, etc. ③ Seizures that cannot be classified: seizures that cannot be classified into the above two categories. Seizure classification is the most important basis for clinicians to choose treatment drugs. For details, please refer to “What does a seizure look like”. (3) Classification of seizures by time of day: There are three types of seizures: ① Sleep epilepsy: Seizures that occur mainly during sleep. There are two peaks of seizure onset, i.e., when sleeping and when waking up. (2) Awakening epilepsy: epilepsy that occurs mainly during waking hours. There are two peaks of onset, i.e., just after waking up and in the evening. (iii) Irregular epilepsy: epilepsy with seizures during both waking and sleeping. Classification by seizure duration is mainly appropriate for generalized tonic-clonic seizures and complex partial seizures. It is useful for initial determination of the cause of epilepsy. Irregular epilepsy is mostly symptomatic; sleep epilepsy is more symptomatic and has common brain tumors; and awakening epilepsy is mostly primary epilepsy. Some seizure types have relatively specific seizure time frames. For example, most of the disoriented seizures are waking epilepsy; benign central-temporal spike-wave focal epilepsy almost always occurs just after falling asleep (sleep epilepsy), etc. (4) Classification according to the difficulty of seizure control: there are 2 categories. (1) Common epilepsy: 80% of the cases. Seizures can be completely controlled with reasonable medication. (2) Refractory epilepsy (also called intractable epilepsy): 20%. Drug treatment is ineffective.