1. not concrete; something that cannot be experienced through the five senses: abstract
Abstract things or phenomenons do not have a physical or concrete existence and therefore they can not be experienced through the five senses. Examples of abstract concepts are liberty, love, beauty, happiness,
2. having two or more possible meanings; not clear: ambiguous
Something ambiguous is something open to more than one interpretation. For example, many people argue that the Bible is an ambiguous book because it does not have one obvious meaning, but several.
3. complicated; not simple: complex
Complex is something that has many different and connected parts or that is not easy to understand. For example, cancer is a complex disease because it is influenced by a combination of multiple genes and environmental factors and needs a multidisciplinary and interdisciplinary approach to be analyzed and understood.
4. showing clear reasoning: logical
Something logical is something in accordance with logic or with clear, sound reasoning. For example, an argument is logical when its conclusion is a logical consequence of its premises.
