In my schedule of learning there are these words and because of their similarity, I seem to mix them up. Any ideas how to make it easier to not do that?
狭い narrow
広い spacious
明るい bright
軽い light
also I notice the い trend, is this for more words?
These are adjectives, and they are one group of adjectives known as い-adjectives. You can recognize them because of the い at the end. But be warned: not all adjectives with い at the end are い-adjectives. This would mean that those are the other type of adjectives, な-adjectives. These are generally the two types of adjectives you'll see often. There's also another type, the の-adjective, but I believe this one is more related to な-adjectives.
To answer your question, ignore the い at the end. The word itself is before the い part. That is the part you'd have to learn to know the word. The い part for い-adjectives have something that other adjectives can't do, and that is that you get to change it when you change tense. The rest of the word however, of course, remains preserved.
