complicated vs complex

Complex (adj.)
– consisting of many different parts and often difficult to understand. A complex process or relationship is difficult to understand because it has lots of parts connected in different ways. The word does focus is on the structure of system and many parts. Complex 指包含許多不同的部分, 因而比較難懂或難解釋的

complex molecules, complex network of roads, complex organizational structure, complex mechanism, complex number, complex mixture, complex ion, complex personality, complex system, complex issue, complex technology, complex process

A complex sentence consists of one or more subordinate clauses and a main clause.

Complicated (adj.)
– difficult to understand, solve, explain and deal with because many parts or details are involved. The emphasis is on understanding and implementation. Complicated 指 “各部分相互交錯而變得錯綜複雜”

Complicated instruction, complicated rule, complicated relationship, complicated arrangement, complicated mess, complicated procedure, complicated situation
complicated medical problem(e.g. complicated appendicitis) ~medical problems involving complications

Complex can be used as a noun and “complicated” is also the past tense and past participle of the verb “complicate”.

These two words are used interchangeably sometimes. It is probably more common to use "complicated" than "complex". Complex sounds more technical.

Nuclear Physics is a complex subject to study because most authors give complicated explanations in their textbooks.

Complex is used to refer to the level of components in a system. If a problem is complex, it means that it has many components. Complexity does not evoke difficulty. (結構)Complicated refers to a high level of difficulty. If a problem is complicated, there might be or might not be many parts but it will certainly take a lot of hard work to solve. (理解,應用)