The tip of the foot (the toes); also the front/tip part of a shoe or sock.
彼はつま先でそっと立ち上がった。
He quietly stood up on his tiptoes.
新しい靴はつま先がきつくて歩きにくい。
The new shoes are tight at the toes and hard to walk in.
バレエの練習で、つま先立ち（つま先立ち）を何度も繰り返した。
In ballet practice, we repeatedly practiced standing on the tips of our toes.