Receptiveness is the quality of being receptive — how willing you are to consider new ideas or to hear someone out. You can talk about a person’s receptiveness, a team’s, or even a market’s receptiveness to a new product (whether buyers will give it a chance). It is the noun; receptive is the adjective. Another noun, receptivity, means almost the same and sounds a bit more academic. This is not reception (a party, or the desk in a hotel), even though the first part looks the same.