Three characters differentiated by the direction of a stroke

子 (zǐ, and also frequently zi [neutral tone]) is a very common character, whose final sideways stroke is horizontal.

孑孓 (jiéjué; mosquito larva) shows that the final sideways stroke can be made both tilting slightly upward from left to right, and also tilting slightly downward from left to right, each change resulting in a different character.

I had long ago seen 孑 (jié) as the left half of characters like 孫 (sūn; grandson) and 孔 (kǒng; hole), but had incorrectly imagined that it was simply a variant of 子 (zǐ) when 子 served as a component part of another character, similar to things I touched on here.