The word 'close' is pronounced differently depending on if it's being used as a verb (use a /z/) or as an adjective or adverb (use an /s/.) Words that are spelled the same but pronounced differently are called heteronyms.
Note the following sentences:
- (verb) Please close the door. /kloʊz/
- (adjective) The window is close to the door. /kloʊs/
- (adverb) She is standing close to the door. /kloʊs/
Words that end in '-ose' are more likely to be pronounced with a /z/ than an /s/. Other examples with a /z/ pronunciation include:
Another word ending in 'ose' that is pronounced with an /s/ is the word 'dose.'