Word of Obligation is a phrase used to describe an obligation or duty that someone is expected to fulfill. It is often used in the context of moral or legal obligations. The two crossword solutions for this term are 'SHOULD' and 'OUGHT', both of which have 6 and 5 letters respectively. Both words are used to express an obligation or duty that someone is expected to fulfill. They are often used interchangeably, but 'SHOULD' is more commonly used in formal contexts, while 'OUGHT' is more commonly used in informal contexts.