1. 复杂的;错综的
    Something that is complex has many different parts, and is therefore often difficult to understand.

    e.g. ...in-depth coverage of today's complex issues.
           对时下一些复杂问题的深度报道
    e.g. ...a complex system of voting.
           错综复杂的选举体制

2. (句子)复合的
    In grammar, a complex sentence contains one or more subordinate clauses as well as a main clause.

3. 综合建筑群;综合大楼
    A complex is a group of buildings designed for a particular purpose, or one large building divided into several smaller areas.

    e.g. ...plans for constructing a new stadium and leisure complex.
           修建新体育场和休闲中心的计划
    e.g. ...a complex of offices and flats.
           商住综合楼

4. 错综复杂的组合;复合体
    A complex of things is a group or system of things that are connected with each other in a complicated way.

    e.g. ...the complex of clans which occupied the land.
           生活在这片土地上的关系复杂的氏族群落
    e.g. ...the military-industrial complex.
           军工综合企业

5. (通常指由于过去不愉快的经历而形成的)情结
    If someone has a complex about something, they have a mental or emotional problem relating to it, often because of an unpleasant experience in the past.

    e.g. I have never had a complex about my height.
           我从来没有担心过自己的身高。
    e.g. ...a deranged attacker, driven by a persecution complex.
           患有受迫害妄想症、精神失常的袭击者