Why is it die Sole?

Sole ends in -e, and most nouns ending in -e are feminine: in a German dictionary, 79% of them take die.

All nouns ending in -e
Sense 1
die

Meaning

[1] Liquid mixture of water and one or more salts

[1] flüssiges Gemisch aus Wasser und einem oder mehreren Salzen

Examples

[1] SOLE is in many cases a healing efficiency

[1] Sole ist in vielen Fällen heilwirksam.

Declension

1 Singular Plural
Nominativ die Sole die Solen
Genitiv der Sole der Solen
Dativ der Sole den Solen
Akkusativ die Sole die Solen

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary