This document discusses the morphological differences between English and Indonesian that cause problems for learners of each language. It analyzes morphological processes, parts of speech, word order, clauses, possession, and complex sentences. The key issues are: 1) Indonesian learners struggle with English morphological replacements and inflections in adjectives/adverbs. 2) English learners have difficulty with Indonesian infixes and flexible word order. 3) Both experience problems with clauses without subjects, possession, and subordinate clauses due to differences in each language.