Final answer:
An acceleration clause allows the lender to demand immediate repayment of the entire loan amount if the borrower defaults on their loan payments or fails to meet certain conditions specified in the agreement.
Step-by-step explanation:
A lender can usually invoke an acceleration clause in a loan agreement if the borrower defaults on their loan payments or fails to meet certain conditions specified in the agreement. An acceleration clause allows the lender to demand immediate repayment of the entire loan amount, instead of the borrower making regular installment payments. This clause is commonly found in mortgage agreements and other types of loans.