(1) I have checked my books, and this is what I have learned:
(a) The word "home" is an exception. (As you know, all languages
have exceptions to the rule.)
(b) When you use "home" with a verb of motion, do NOT use a
He went home.
He came home.
I was home by six o'clock. (In this sentence, "was" is like a verb of
motion because it = I came home by six o'clock.)
For "perfect" English, you should say:
Tom is not AT home. (You should use "at" because there
is NO idea of MOTION -- moving.)
But in regular English, everyone usually says:
Tom is not home.
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