According to the BABOK Guide, textual requirements are one of the forms of specifying and modeling requirements. Textual requirements are written statements that describe the characteristics of the solution in a clear, concise, and consistent manner. Textual requirements typically consist of three components: the capability of the solution, the condition under which the requirement is applicable, and the constraint that may limit the solution. The capability describes what the solution must or should do, the condition describes the situation or scenario in which the requirement is relevant, and the constraint describes the restriction or limitation that may affect the solution’s ability to meet the requirement. For example, a textual requirement for a banking system could be:

The system shall allow customers to withdraw cash from any ATM machine (capability) within the network (condition) up to a maximum of $500 per day (constraint).

References:

[A Guide to the Business Analysis Body of Knowledge (BABOK Guide)], version 3, page 402, section 10.31.2.11

Textual Requirement Artifacts - Blueprint Online Help - HelpDocs, paragraph 1

How to Model Textual Requirements - Formal Mind GmbH, paragraph 2