Synergy is interaction of two or more system elements that produce a combined effect greater than the sum of their separate effects. The additional effect or the difference that is created from such an interaction is called synergy effect or synergistic effect. A system can be economical, technical or others. The effect of synergy can be both positive and negative. The positive synergy is sometimes expressed as ‘2+2=5’ effect or ‘1+1=3’ effect, negative synergy is expressed as ‘2+2<4’ effect. The negative synergy effect is called dissynergy, zero synergy effect or asynergy. The global population is growing and it has an impact on the environment. In connection with the limited resources and the not limited human needs, it is necessary to save resources. To ensure that there are enough food, water and wealth in future, we need to switch from a linear to a circular economy. The goal is to ensure healthy and safe living and working conditions and cause less harm to the environment. The highest synergy is identified between green economy and circular economy, which can provide sustainable development in an urban environment and rural areas. Additionally, all of these relations are part of geoeconomics.