Post, as in postcard.
card or carl
post = signpost.
card box code haste post
card care carp cars
The answer is post, to make postcard, postbox, postcode, postbag, and posthaste.
post
Post.
Cart Colt Cram Card Cats Cite Clam Cold
A four letter word starting with the letter a is able.
card, box, code , bag, haste
It depends on what you mean by 'four letter word'. Thea has four letters, so yes it is. It is not a swear word, so it's not that kind of 'four letter word'.
A four letter word for 'in addition to' is also.