Hi, Mark Lewis : Denis Mosko!
I read your message from 20.03.2019 19:43

 DM>> Correct, please:
 DM>> The cat, which walking by herself.
 ML> that looks like an incomplete sentence but if it isn't, i'd use
 ML> The cat was walking by itself.
 ML> i used "itself" since we don't know the sex of the cat... but if we
 ML> do, then "himself" for male or "herself" for female is OK...

I thought that in English "cat" is male, like a ship is female. 

"The cat, which walking by herself," is probably taken from a story for
children, where they are told how the cat had become a domestic animal. The cat
 there could talk, and when the ancient woman invited him into the cave, he
always replied, "I am a cat. I am walking alone and everywhere I want to." ;-)
Do you have this story in the English literature?

Bye, Mark!
Alexander Koryagin
english_tutor 2019

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