Mutual reception
Two planets are in mutual reception when each occupies a sign the other rules, an exchange that classical astrology reads as mutual assistance between them.
Mars in Cancer with the Moon in Aries is the standard example: each is a guest in the other's house, so each is in a position to help. Neither planet gains dignity from the arrangement, which is the common misreading; what it gains is a working relationship.
Reception by exaltation, triplicity, term or face is also recognised, weakening as it descends the tiers. The strongest form, by domicile, is what the term usually means without qualification.
Frequently asked
Does mutual reception fix a debilitated planet?
No. It does not add dignity. It gives two planets a way to work together despite their condition.
Do the two planets need to aspect each other?
Classical authors prefer it, and a reception with an aspect is treated as considerably stronger than one without.