Saif is an Arabic name for boys that means “summer”, if spelled as صَيْف in Arabic. If spelled as سَيْف, it becomes a non-Quranic word that means “sword”. Both are acceptable as names, and both have nearly the same pronunciation in English. The difference is that for the meaning of “summer” the “s” sound in Saif is made further back in the mouth, similar to how the “s” in “some” is different from the “s” in “sit”.