Scrabble rule-I can't remember why this didn't work

I played AUTO across the trip at the bottom center, next draw I had the tiles to make it AUTOMATION, to the next trip, but it wasn’t allowed. I cannot remember the rule for that–too many letters??

That sounds legal to me: the new letters MATION are in one line, and added to letters on gthe board frm a valid word.

Your opponent could have argued that you should have been allowed to play auto in the first place. It’s an abbreviation of automobile, no?

Are you saying you weren’t allowed to play the word at all, or that you didn’t get the triple word score?

If it’s the former, I expect it’s because AUTOMATION isn’t in the official Scrabble dictionary (4th edition, 2005). AUTOMATE, AUTOMATED, AUTOMATING, and AUTOMATES are.

I believe OSPD maxes out at 8-letter words. Whereas all the other examples are simple verb tenses of AUTOMATE, and would therefore be listed, AUTOMATION is a separate word, and would not be. That doesn’t mean it’s not playable, just you need a different word list for longer words.

“… it wasn’t allowed” sounds like OP was playing on a computer. If the word was not allowed, it may be that the program only has the OSPD words (2-8 letter base word, with other forms of the SAME word), or excludes anything longer than a certain length.

There is no rule in Scrabble limiting the length of words. I once extended “EXHAUST” to “EXHAUSTIONS” without incurring a penalty.

On various online Scrabble fora, I have seen people complain about Words With Friends or Facebook Scrabble declaring that some perfectly valid word was disallowed because it was mistakenly left off the word list.

You’ll need a computer for this, so if your Scrabble playing is confined to handhelds, it won’t work. ISC.RO (International/Internet Scrabble Club, based in Romania) is a site where you can download their (IRC, IIRC) client and sign up to play other players live. Unlike many Scrabble simulations, you will be limited to two players in any game – just like tournament play. But the (US) dictionary seems complete, despite the copyright on the latest word list approved by Hasbro.

The best (that I know of) Scrabble bot is Quackle, but I do not know if they have been granted the ability to use the new, copyrighted word list that became effective immediately after the 2014 National Championship.

As an aside, the official rules of the board game do not specify any particular dictionary to use, and only require that all of the players agree to a dictionary. There’s one particular dictionary that competitors in tournaments typically agree to use, but that doesn’t mean you’re “doing it wrong” if you and your opponents choose to use a different one.