successive generations of a family etc. / (geology) eon

芽: bud, sprout, shoot / 芽: the germ of an idea, an inkling / 芽: (biology) a bird embryo: more specifically, as found on the yolk of an egg, the blastodisk, the germinal disk, the embryonic disk

単車: a motorcycle, motorbike / 単射: an injective function / 炭車: a minecart for carrying coal

dent, hollow