For English as a Second Language (ESL) students or English Language Learners (ELLs), the use of various adverbial clauses was summarized and illustrated of comparison, concession, condition, degree, manner, place, proportion, purpose, reason (or cause), result, and time, including the non-finite clauses, some prepositions, and prepositional phrases, from multiple examples cited or given, on the basis of the writer's extensive review of different English grammar books, reference books, magazines, newspapers, books, English dictionaries, and online articles, in order for ESL students and ELL learners to further understand how to use them appropriately. The goal of this article is that it will serve as a guide for ESL students and ELL learners and their teachers.