Merriam-Webster Collegiate Dictionary - should

 verbal auxiliary, past of shall  Etymology: Middle English sholde, from Old English sceolde owed, was obliged to, ought to  Date: before 12th century  1. — used in auxiliary function to express condition if he ~ leave his father, his father would die — Genesis 44:22 (Revised Standard Version)  2. — used in auxiliary function to express obligation, propriety, or expediency 'tis commanded I ~ do so — Shakespeare this is as it ~ be — H. L. Savage you ~ brush your teeth after each meal  3. — used in auxiliary function to express futurity from a point of view in the past realized that she ~ have to do most of her farm work before sunrise — Ellen Glasgow  4. — used in auxiliary function to express what is probable or expected with an early start, they ~ be here by noon  5. — used in auxiliary function to express a request in a polite manner or to soften direct statement I ~ suggest that a guide…is the first essential — L. D. Reddick