There are three main points summarized from the document:
1. Contrastive analysis (CA) can be used to predict areas of difficulty for language learners, diagnose errors, and inform test and course design by comparing the learner's first language (L1) with the target second language (L2).
2. There are two types of CA - theoretical, which looks at universal linguistic categories in L1 and L2, and applied, which focuses on how a category in L1 is represented in L2. Applied CAs are used more directly for language teaching.
3. CA can predict difficulties, errors, and the tenacity of errors. However, it is limited in the number of errors