【Promise】 ,  【engage】 ,  【pledge】 ,  【plight】 ,  【covenant】 ,  【contract】  are comparable when they mean to give one’s word that one will act in a specified way (as by doing, making, giving, or accepting) in respect to something stipulated.

【Promise】 implies a giving assurance either orally or in writing but it suggests no further grounds for expectation of the fulfillment of what is promised.

【Engage】  implies a more binding agreement or more definite commitment than  【promise】 . Typically it is used in formal or consequential situations, sometimes specifically implying an agreement to marry and sometimes an agreement to accept as an employee. It ordinarily implies a 【promise】 regarded as binding and to be relied on and especially one concerning conduct over a period of time.

【Pledge】  (compare  【PLEDGE】  ), aside from uses in connection with drives and charities, may imply the giving of a 【promise】 by some act or words that suggest the giving of a solemn assurance or the provision of a formal guarantee.

【Plight】 implies a solemn promising and persists chiefly in a few stereotyped phrases such as " 【plight】 one’s troth."

【Covenant】 implies at least two parties to the 【promise】 , each making a solemn agreement with the other.

【Contract】  (see also  【CONTRACT】 3 INCUR ) implies the entry into a solemn and usually legally binding agreement (see  【CONTRACT】  ).