Waste: This is a loss connected with raw material or inputs to the production process and usually means to refer that input has been lost due to any reason either because of its nature of the material itself, nature of the process or some other conditions. Sometimes such output that does not have any sales or use is also referred as waste.
For example in paint industry many chemical are used that are volatile i.e. can evaporate at room temperature. Another example can be of break-oil which is wasted in the process named “bleeding” in which air bubbles are removed from the pressure pipes so that hydraulics can work effectively.
Scrap: This is a loss connected with the output. Most of the time at the end of production/conversion process such outputs are generated that were not intended but cannot be eliminated due the nature of material or process itself. Usually they are of no to insignificant value as compared to the main product that was intended. We usually know them with the term by-products. This is considered as loss as not all of the raw material is converted into intended product.
For example in furniture manufacturing chippings of wood and sawdust is a common example. Another very known example is of gold dust in jewellery and gold industry.
Spoil: This is also a loss connected with the output. In the production process if the output is produced which is not up to the quality standard due to any problem and now the product cannot be brought back in good state even after further processing or reprocessing or it is simply not feasible to do so then such output is called spoil or spoiled output or spoilage. This is considered as loss as it is such finished good which is not worthy of sale and thus cannot generate intended revenue.
For example in fashion and clothing industry many of the well known brands have strict quality standards which if not met then product is not considered to be worthy to a regular retail outlet and is most of the time shredded or sold as “B” pair or “seconds”.
Defect: This is another type of loss connected with the output but it can be in the input as well. This is close to waste but with the difference that it is such output which does not qualify all the quality standards due to some problem but that problem CAN be fixed by further processing or reprocessing and it is also feasible to do so. This is considered as loss as more then normal effort will be required to bring the goods into saleable condition.
For example in juice manufacturing industry where juice is not sweat up to a required level or is not homogenized to give a required molecular level thus not consistent enough. Another example can be car repair and maintenance where sometimes paint dries too quickly thus not giving proper shine and will have to be “touched” again.