Conjunction
Two planets at the same zodiac degree, zero degrees apart. Their agendas fuse and act as one, for better or worse depending on the pair. The strongest aspect there is.
A conjunction is two bodies at the same ecliptic longitude, usually side by side in the same sign, occasionally close enough to admire as a single point of light. The great Jupiter and Saturn meeting of December 2020 was a conjunction you could see from a parking lot.
In a chart, conjunction means fusion. The two planets stop taking turns and act as one blended thing, which is splendid or awkward depending on who is blending: Venus with Jupiter mixes easily, Mars with Saturn grinds. A conjunction is not a good or a bad aspect. It is a strong one.
The Moon and Sun conjoin every month; that is the New Moon, and it is the template for reading conjunctions in time: something starts, quietly, and grows from there.
See also