The letter of the law is no contractions. BF says "key items may not correspond to short forms or contractions". I read that to mean a key cannot be just the 'ar' contraction. If you used v(ar) as a key, the key does not correspond to a short form or a contraction. So it depends on if you want to follow the letter of the law or the spirit. 🙂 There is a lot of disagreement on this. Choose and then be consistent. And be sure you do not form a word - for instance, the key should NOT be c(ar) as that forms the word 'car'...that's one of the reasons this rule is in place. Keys need to be clearly NOT part of the text. If you wanted your key to be c-a-r (three letters) it can be - just uncontracted so it is not the word 'car'. Again, some will disagree with me but the rule IS open to some interpretation.