Term Description Further Details
Flash All current discharges and electrical impulses from a lightning event. Generic Terms.
A Flash can occur within clouds (CC) or between a cloud and the groune (CG)
A Flash can be composed of one or many Strokes.
A Flash combines current discharges that are detected in LF and electrical breakdowns that are detected in VHF
Stroke or return stroke Electrical discharge in a lightning flash to earth  
First stroke First stroke of a cloud to ground flash  
Subsequent stroke All the remaining strokes after the 1st one (the 2nd, 3rd, …) in a cloud to ground flash  
Flash A shortcut to define a flash by its first stroke. The first stroke is used to represent a group of strokes
Intra-cloud Discharge of intra-cloud current Between two clouds (CC) or within the same cloud (IC)
VHF lightning Set of electrical bursts in an event
Generic term.
A VHF flash is an intra-cloud phenomenon, it is made of bursts that can be grouped in branches
Source (or burst or breakdown) Emission of an electrical burst Only detectable in VHF
Branch (or ramification) Grouping of the sources belonging to one flash, used to draw their development in space and time Group of VHF sources represented in the form of branches
Flash Extent
Contour of the sources belonging to a single flash
Represented by a polygon or an ellipsis
Source density Number of sources as computed on a grid for a given time period Represented by a grid or a surface