Pappy,
Wow! Isn't that the truth. Example - I never use the word "tool" - my spell check always turn it into *****, ah, ha.
This is the best and most accurate definition going so far. It really makes a lot of sense as any thing attached would assume some bolted connection not just a couple of pins like an implement would be.Here is the answer (IMO) :
"Implement" is the broad, general term that includes all equipment, attached or towed; "Attachments" are a sub-category of implements and would generally includes things mounted on the tractor that are not towed. i.e. All attachments are implements, but not all implements are attachments.