Design for excellence (DfX or DFX) is a term and abbreviation used interchangeably in the existing literature, where the X in design for X is a variable which can have one of many possible values. In many fields (e.g., very-large-scale integration (VLSI) and nanoelectronics) X may represent several traits or features including: manufacturability, power, variability, cost, yield, or reliability. This gives rise to the terms design for manufacturability (DfM, DFM), design for inspection (DFI), design for variability (DfV), design for cost (DfC). Similarly, other disciplines may associate other traits, attributes, or objectives for X.

Under the label design for X, a wide set of specific design guidelines are summarized. Each design guideline addresses a given issue that is caused by, or affects the traits of, a product. The design guidelines usually propose an approach and corresponding methods that may help to generate and apply technical knowledge to control, improve, or even invent particular traits of a product. From a knowledge-based view, the design guideline represents an explicit form of knowledge, that contains information about knowing-how-to (see Procedural knowledge). However, two problems are prevalent. First, this explicit knowledge (i.e., the design guidelines) were transformed from a tacit form of knowledge (i.e., by experienced engineers, or other specialists). Thus, it is not granted that a freshman or someone who is outside the subject area will comprehend this generated explicit knowledge. This is because it still contains embedded fractions of knowledge or respectively include non-obvious assumptions, also called context-dependency (see e.g. Doz and Santos, 1997:16–18). Second, the traits of a product are likely to exceed the knowledge base of one human. There exists a wide range of specialized fields of engineering, and considering the whole life cycle of a product will require non-engineering expertise. For this purpose, examples of design guidelines are listed in the following.