Which of the following describes a foreign key in entity relationships?

A foreign key is a crucial concept in database design, playing a vital role in establishing relationships between tables (or entities). It is defined as a field (or a set of fields) in one table that uniquely identifies a row of another table. When we refer to a foreign key as a link to a single row in another entity, it signifies that it creates a one-to-many relationship between the tables involved, where the foreign key in the first table corresponds to the primary key in the second table. This enforces referential integrity, ensuring that relationships between the entries in the tables are valid.

In a typical use case, the foreign key links a record from one table (the child or referencing table) to a specific record in another table (the parent or referenced table). For instance, if you have a table for 'Orders' that contains a reference to a specific 'Customer', the foreign key in the 'Orders' table will point to the 'Customer ID' in the 'Customer' table. This effectively allows one customer to be associated with multiple orders while each order can be clearly linked to only one customer.

The other options do not accurately encapsulate the essence of a foreign key. While a foreign key does create relationships between tables, it