Online Encyclopedia of Western Signs and Ideograms Symbols.com

Symbol 4:6

0405

04:6 · This is the same structure as the chevron, but with a much sharper angle. It is used in logic to signify all that lacks existence, nothing, or the empty class. An ideographic opposite is 2601a, and a semantic opposite is the entry sign below.
    0405 is also used to denote the concept and when used between signs for entities in logic.
    Otherwise 0405 denotes an upwards directed movement in the same way as does 0419.