Am I right to think that cornmeal consists of corn granules with 2-3mm diameter, and is used e.g. in grits? If so, meal is MaisGriess , here's Migros for the less posh. The local siblings of grits are Riebel (traditionally made from RiebelMais, a particular corn variety from the Rhine valley) and Polenta (culturally appropriated from Italy).
The first is gluten free cornflour, the 2nd cornstarch. Both organic.
I don’t know the exact measurement, but corn meal is gritty to the touch and corn flour is silky, like powder. In the US, corn flour is often called corn starch. I think corn flour is more commonly used in UK English, and probably more commonly used in Asian translations. It can be confusing.
Corn meal is also mesa harina (have I spelled that correctly) in Mexican cooking.
Check the nutrients. Flour has mostly carbs but also significant amounts of proteins, fibers and fat, whereas starch contains pretty much carbohydrates only. At least around here Maizena is the default and ubiquitous cornstarch thing. Careful though, some sauce thickeners (Maizena Express) use the Maizena label, too, their USP is that they can be added directly (rather than in a slurry) without risking clumps.
Masa is actually different. For Masa the dried maize kernals are soaked in calcium hydroxide before grinding which changes the taste.
Agreed. For tortillas you would want masa harina , probably also available at El Mais (I would hope!).