Requirements Defects:

• Requirement related defects arise in a product when one fails to understand what is required by the customer.
• These defects may be due to customer gap, where the customer is unable to define his requirements, or producer gap, where developing team is not able to make a product as per requirements.
• Defects injected in early phases can persist and be very difficult to remove in later phases. Since any requirements documents are written using natural language representation, there are very often occurrences of ambiguous, contradictory, unclear, redundant and imprecise requirements.
• Specifications are also developed using natural language representations.

Design Defects:

• Design defects occur when system components, interactions between system components, interactions between the outside software/hardware or users are incorrectly designed. This covers in the design of algorithms, control, logic/ data elements, module interface descriptions and external software/hardware/user interface descriptions.
• Design defects generally refer to the way of design creation or its usage while creating a product. The customer may or may not be in a position to understand these defects, if structures are not correct.
• They may be due to problems with design creation and implementation during software development life cycle.