Student or Learner
Is there any term for "parking space" which is flat, non-mechanical?...Could I say it as "on-grade" or "plane" parking space, or something else?...
Perhaps you mean plain In that case you could also say 'ordinary', 'common or garden' [somewhat jocular], or 'run-of-the-mill'. Maybe even 'standard'. Sometimes, when you are talking about the most basic form of a product, with no extras, you can call it 'vanilla' - but I can't imagine that word being used to refer to a parking space! Example [someone phoning a computer help desk]: 'I'm using vanilla Internet Explorer with no plug-ins - just out-of-the-box IE as it came pre-installed on my laptop, and it can't...' [I leave the rest to your imagination; there are so many possibilities!]