I review papers on the subject of Process Intensification (PI). Often the researchers struggle with the proper use of terms. I also give a course on PI for industrial chemical engineering practitioners. In some cases, participants struggle with the meaning of terms used. I therefore made a brief list of terms misunderstood or misused in the Process Intensification field. For each term I give a definition and for some terms also a reference. Here it is.
Process Intensification is a set of radically innovative process design principles which can bring significant benefits in terms of efficiency, cost, product quality, safety, and health  over conventional process designs based on unit operations .
Modular design is a detailed process engineering design of modules, which can be easily connected to each other (plug in principle), The modules are detailed process engineered and constructed by an Engineering Procurement Construction (EPC) company . Each module can be constructed many times using the same detailed design .
Skid mounted means that the process plant or modules are constructed inside a skid frame. The process plant is constructed at the EPC company, dry tested and then transported to the manufacturing site . Most modular designed processes are skid mounted.
Distributed process plants means that many small capacity process plants are distributed over various locations.
To keep the investment cost per ton of product at acceptable levels often the process concept design is based on process intensification methods, while the detailed process engineering is based on modular design and the construction is skid mounted.
Conventional Stick Built is the conventional constructing the process plants at the manufacturing site. It is the opposite of modular design with skid mounted construction.
Building Blocks are the process intensified versions of unit operations of a process design. .
Functional process design is conceptual process design based on functions and function integration [2,3] rather than on established unit operations.
Numbering up is a term used my many people and often each mean something different. The presenter may mean having many of the same equipment pieces parallel to each other but connected to the same input and output device. The presenter may mean having process trains in parallel to each other on the same manufacturing site. The presenter may mean a linear investment cost curve with production capacity. Often the last meaning is wrongly connected to the other meanings. Even with parallel process trains the total investment cost correlates in most case with the capacity to a power less than 1. As a lot of construction cost, such as buildings, concrete floors, pillars, and others are still shared. So, ask for clarification when “numbering up” is used.
 Stankiewicz. A, Gerven, van T. Stefanides, G, The fundamentals of process intensification, Wiley-VCH, Weinheim, 2019.
 Harmsen, J, Verkerk, M, Process Intensification, De Gruyter, Berlin, 2020.
 Harmsen J, Verkerk M, A New Approach to Industrial Innovation. CHEMICAL ENGINEERING PROGRESS. 2021 Mar 1;117(3):50-3.