Why is it die Kandidatin?

Kandidatin ends in -in, and most nouns ending in -in are feminine: in a German dictionary, 88% of them take die.

All nouns ending in -in
Sense 1
die

Meaning

[1] A female person who is available for something

[1] eine weibliche Person, die für etwas zur Auswahl steht

Examples

[1] Ms. Müller was a candidate for the first time in a game show

[1] Frau Müller war erstmals Kandidatin in einer Spielshow.

[1] The two candidates for the temporary position have presented both excellent references

[1] Die beiden Kandidatinnen für die Aushilfsstelle haben beide ausgezeichnete Referenzen vorgelegt.
More source examples (1)

These dictionary examples can include historical and less common uses.

[1] "So it was probably two hours until all three candidates had presented every conceivable emotion on the emotional scale"

[1] „So ging es wohl weitere zwei Stunden, bis alle drei Kandidatinnen jede nur denkbare Regung auf der Gefühlsskala dargeboten hatten.“

Declension

1 Singular Plural
Nominativ die Kandidatin die Kandidatinnen
Genitiv der Kandidatin der Kandidatinnen
Dativ der Kandidatin den Kandidatinnen
Akkusativ die Kandidatin die Kandidatinnen

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary