noun
multitudinousness; vast number; countless
Rare, literary noun expressing an overwhelmingly large number or multitude. Not used in everyday conversation; found in classical or poetic contexts.
夜空には百千万の星が輝いていた。
A countless number of stars shone in the night sky.
幾千万 also means 'myriads' or 'tens of millions', but is more common and can be used in modern writing.
Compound of 百 (hundred), 千 (thousand), and 万 (ten thousand), literally 'hundreds, thousands, and ten-thousands', emphasizing an immense number. The exact historical derivation is uncertain.