Vocabulary consisting only from characters you are able to read
鼠
nezumi
(1)mouse, rat, (2)dark gray, dark grey, slate (color, colour); (3)mouse, rat, (4)dark gray, dark grey, slate (color, colour) doubutsu
十億
juuoku
1,000,000,000, billion (American), (obs) milliard (British)mix
主に
omoni
mainly, primarilymix
主な
omona
chief, main, principal, importantmix