Learn how to say Spontaneousness correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word spontaneous:
performed or occurring as a result of a sudden impulse or inclination and without premeditation or external stimulus:
the audience broke into spontaneous applause
a spontaneous display of affection
having an open, natural, and uninhibited manner.
(of a process or event) occurring without apparent external cause:
Biology (of movement or activity in an organism) instinctive or involuntary:
the spontaneous mechanical activity of circular smooth muscle
archaic (of a plant) growing naturally and without being tended or cultivated.
mid 17th century: from late Latin spontaneus (from (sua) sponte ‘of (one’s) own accord’) + -ous
Remember that spontaneous ends with -neous.