In North America, there is actually a flour, not a starch, called corn flour. Corn flour is made from cornmeal that has been made from dent corn, then further ground up so finely that it no longer looks or feels like grains of sand (as cornmeal does), but instead is powdery like a flour.
Masa Harina is a type of corn flour, though not made from cornmeal.
Note that in the British sense of the word, a starch, there is no space used between the two words, whereas in the North American sense there is. While this is a reasonable guideline to telling which a recipe writer means, you can’t count on it as people writing up recipes in a hurry could spell it either way, especially as the Internet blurs boundaries more and more. A better way of telling which is meant is looking at the quantities involved: if a recipe calls for quantities in the range of 1/2 pound or 200 g corn flour, chances are it doesn’t mean cornflour, as in the starch.
Corn flour can be used in making bread, but as it will produce no gluten, you will need to take the usual necessary measures of either expecting a flat bread or adding wheat flour as well.
Grind cornmeal in your blender until you have enough that is the powdery consistency of flour.
30 g (1 oz) = 1/4 cup = 4 tablespoons
Refrigerator or freezer