Orb
How many degrees an aspect can miss its exact angle by and still count — a margin, not a strict, all-or-nothing cutoff.
Aspects are rarely exact to the degree; an orb is the allowed range on either side of the exact angle that still counts as the aspect being active. A conjunction two degrees apart still reads as a conjunction, just a slightly looser one than a conjunction a tenth of a degree apart; go wide enough and eventually the contact fades out rather than switching off all at once. Different traditions use different orb sizes, tighter for a fast-moving personal point, wider for a slow outer planet or a major luminary like the Sun. This site's exact aspects are calculated to the precise instant they're truly exact, to the second, rather than left inside a wide, approximate window — the orb concept still matters for reading a static chart, even where the exact moment itself is known precisely.