Learn English – What’s the difference in meaning between “act a certain way” and “act in a certain way”

"Commodity" has a special meaning as a raw product that is generally the same from one batch or producer to the next. While you can can buy a pound of a particular brand of pinto beans from the grocery store, pinto beans are traded in the stock market in much larger quantities based on a "commodities" price.

You might hear the phrase "a rare commodity". That kind of twists the meaning to suggest that the thing is special. Patience is a rare (valuable) commodity in teachers.

"Products" and "goods" (in that sense) are fairly interchangeable words. Product has a bit more sense of specificity. Peanut butter is among the goods typically found in grocery stores, Skippy peanut butter is one of the products you might find on the shelf. You're more likely to see "goods" (plural) than a "good".

Word for word means you've committed it to memory exactly. If you recite it, every single word will be exactly correct, the same as the words you read earlier. This phrase is about accuracy.

Word by word means that you memorized it one word at a time. It's more about the method you used while memorizing than the accuracy of the result.