der, die oder das Tochter?

Exception

-er → der

Usually 81.3% of the 2,315 common nouns ending in -er take der.

Tochter breaks this rule: it is die Tochter, not der Tochter.

This is only a tendency. Common exceptions are family words (die Mutter, die Tochter) and das Zimmer, das Fenster.

Other exceptions die Mutter, die Schwester, das Wasser, das Alter