What is another word for complex

A straightforward antonym for 'complex' is 'simple.' This term directly contrasts with the idea of being made up of many parts or being difficult to understand, instead referring to something easy to understand or composed of a single element.

Yes, 'plain' can be considered an antonym for 'complex.' While 'plain' primarily denotes something without adornments or without much variation, it contrasts with 'complex' by suggesting something straightforward, easily understood, or lacking in complicated features.

'Straightforward' is indeed a valid antonym for 'complex.' It is particularly used in contexts where 'complex' describes situations, processes, or explanations that are complicated or convoluted. 'Straightforward' implies that something is easy to understand or deal with, lacking in complexity or nuance.

'Elementary' functions as an antonym for 'complex' by denoting something fundamental, basic, or easily understood. It is often used in educational contexts or to describe the initial levels of understanding that do not require the comprehension of more detailed or complicated concepts.