Learn in the textbookRisk Management and Response Strategies
DefinitionAcceptance (受容) is the response of taking no steps to reduce a risk and deciding to absorb the loss yourself if it occurs.
ExplanationIt is chosen for risks judged unlikely, low in impact, or not worth the cost of a countermeasure. Besides preparing nothing at all, setting aside spare budget or days in advance for use if the risk occurs also counts as acceptance. Money kept aside for events that might happen but are not certain is called a contingency reserve (コンティンジェンシー予備).
AnalogyIt is like living with a small scratch on your phone screen because fixing it is not worth the money, while keeping some savings aside in case the screen ever cracks.
Memory hookIts other name, retention (保有), means you keep the risk in your own hands. Learn the pair: if someone takes it off you, that is transfer; if no one does, that is acceptance.