Lassie vs. Lassy — What's the Difference?

Lassie is a fictional female Rough Collie dog, and is featured in a short story by Eric Knight that was later expanded to a full-length novel called Lassie Come-Home. Knight's portrayal of Lassie bears some features in common with another fictional female collie of the same name, featured in the British writer Elizabeth Gaskell's 1859 short story "The Half Brothers".

A lass.

A young girl, a lass, especially one seen as a sweetheart.

A young girl; a lass.

A girl or young woman who is unmarried