Strong verbs have been growing less and less common over the centuries, because their conjugations are more complicated than weak verbs and harder to predict. That means many verbs that were strong in Old English times are now weak. These include walk, sleep, help, laugh, step, sneeze, chew, wash, shine, climb, let, bake, lock, read, drag, bark, sweep, float, bow, row, fart, creep, flow, starve, weep, grip, leap, mow, slay, shove, carve, gnaw, braid, flee, fare, ban, wreak, quell, delve, abide, yield, spurn, thresh, swell, milk, suck, burst, load, melt, and swallow. Two of these even became weak during the Old English period: sleep ("slǣpan") and read ("rǣdan").