Read in younger son’s physics homework the other day: “The bench moves you fastly to the start and then slowly back through the…”
Nothing to do with hadrons or black holes, fortunately.
Me: “There’s no such word as ‘fastly’.” 
Him: “Yes there is. What’s wrong with fastly?” 
Me: “The word’s ‘fast’. But that doesn’t really work there; you can use ‘rapidly’ or ‘quickly’ but not fastly.” 
Him: “‘Slow’ and ’slowly’ are OK so what’s wrong with ‘fastly’?” 
Me: “It’s just not English. Perhaps the DofE had a point when he asked if you could read and write.” 
The conversation progressed on those lines. I eventually won.
It reminded me, though, of some other ‘…ly’s and various dislikes. An English (or maybe it was a Latin) teacher once told me that Firstly was unacceptable and I should use First instead, which I’ve always done since then. In fact there’s nothing strictly wrong with Firstly; it’s just that some people think its use is ugly.
And then something reported on ‘Quote Unquote’ many moons ago popped into my mind. Two Oxford academics, whilst walking through some college grounds, were heard to say “…and seventhly…” Perhaps they were discussing particle physics.
Then there’s scientific reportese. I hate (no, I loathe) brackets in scientific prose. They always seem to enclose something that the author has forgotten to say or is too lazy to write another way so I go through my colleagues’ reports with that handy little edit function in Word and take out all those brackets that they really don’t need. Thinks: perhaps there’s a reason they don’t want to send me reports to edit?
What else? Well, there’s Substrate and there’s Substratum. Chemists know what substrate means and marine ecologists know about the substratum. Or do they? They seem to be interchangeable on the internet but I’ve always thought the -ate one is to do with enzymes and the -um version is the rock/sand/mud/whatever on which an animal lives.
More red pen. They get their own back with my reports, though.
Over here (USA) the sports commentators always talk about a team or a player’s “quickness”. And no one bats an eyelid.
Quickness - now you mention it, I think perhaps the sports commentators over here say that too. And fastly may be growing on me.
Momentarily is a -ly that I really don’t like. Over here they use it to mean “for a moment” as in “I left the room momentarily”. We use it (correctly of course) to mean “in a moment”, as in “I shall be leaving momentarily”.
I think that’s right, anyway. I try to avoid using it, since I can never quite remember which way round is which!
I’ve been browsing the booklets on writing that the Guardian have produced this week and it seems that I’m just not allowed to use ‘just’ and ’seem’ any more, nor adjectives or adverbs. Add those to ‘got’ and ‘nice’, ‘firstly’, ‘momentarily’ and a whole bunch of other things and I begin to wonder what I’m left with. Or should that be ‘with what I’m left’. Perhaps not.