What is the different between seizure and convulsion ?!

Seizure is : Medical term for specific brain condition, whereas convulsion can mean any muscle contraction, in general usage of the two words. In lay terms, convulsions can mean same thing as a generalized seizure.

Specifically: A seizure refers to an episode of altered consciousness due to an electrical dysfunction of brain, and their are numerous variations. More than one seizure would be termed epilepsy. A convulsion or grand mal seizure, is an episode of diffuse tonic-clonic shaking with or without tongue biting, bowel/ bladder incontinence and subsequent confusion.

Convulsion a subtype: Most consider a convulsion to be a "grand mal" or generalized tonic clonic seizure (primary or secondary). A convulsion is one type of seizure. Some other seizure types include: focal motor (a limb shaking), focal sensory (limb tingling), focal with altered awareness, or absence (short episodes of altered responsiveness often with eye blinks). There are others.

Many types of seizur: A convulsion is a form of seizure. However not all seizures are convulsions.