sure

英 [ʃɔː; ʃʊə] 美 [ʃʊr]

sure: sure: [14] Sure and secure are doublets – that is to say, they come from the same ultimate source, but have diverged over the centuries. Latin sēcūrus (etymologically ‘without care’) was borrowed directly into English as secure, but in Old French it evolved into sur, from which English gets sure.
=> secure
sure (adj.): early 13c., "safe against attack, secure," later "firm, reliable" (c. 1300); "mentally certain, confident" (mid-14c.); "firm, strong, resolute" (c. 1400), from Old French seur, sur "safe, secure; undoubted, dependable, trustworthy" (12c.), from Latin securus "free from care, untroubled, heedless, safe" (see secure (adj.)). Pronunciation development is that of sugar (n.).

As an affirmative meaning "yes, certainly" it dates from 1803, from Middle English meanings "firmly established; having no doubt," and phrases like to be sure (1650s), sure enough (1540s), and for sure (1580s). The use as an adverb meaning "assuredly" goes back to early 14c. Sure-footed is from 1630s, literal and figurative; sure thing dates from 1836. In 16c.-17c., Suresby was an appellation for a person to be depended upon.

1. But legal experts are not sure if such a charge can stick.: 但法律专家们不能肯定这一指控是否成立。

3. If something's a sure-fire hit then Radio One will play it.: 如果哪首歌一定会火，那么第一频道肯定会播出。

4. They want to make sure the newcomers don't get a look-in.: 他们不想让新人有露脸的机会。