One noun is substituted for another which it is closely exaggerated.
Answer:
A prime number is a whole number greater than 1 whose only factors are 1 and itself. A factor is a whole numbers that can be divided evenly into another number. The first few prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23 and 29.
Answer:
sign (one's name) at the end of a document, etc. ... to write one's signature on (a document, etc.) as an indication of consent, approval, attestation, etc.