From friendly + -ness.

• IPA: /ˈfɹɛndlinəs/

friendliness (uncountable)

1. The quality of being friendly.

   Synonyms: affability, amicability, bonhomie, geniality, pleasantness

   Antonyms: hostility, unfriendliness

   • 1878, Robert Louis Stevenson, “Down the Oise: To Moy”, in An Inland Voyage, London: C[harles] Kegan Paul & Co., […], →OCLC ↗, page 141 ↗:

     Finding us easy in our ways, he […] told me a cock-and-bull story with the moral of another five francs for the narrator. The thing was palpably absurd; but I paid up, and at once dropped all friendliness of manner, and kept him in his place as an inferior with freezing British dignity. He saw in a moment that he had gone too far, and killed a willing horse; his face fell; I am sure he would have refunded if he could only have thought of a decent pretext.

• French: gentillesse, cordialité
• German: Freundlichkeit
• Portuguese: cordialidade, amizade
• Russian: дружелю́бие
• Spanish: amigabilidad