leaf / lief are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
leaf: (noun) the main organ of photosynthesis and transpiration in higher plants. (noun) a sheet of any written or printed material (especially in a manuscript or book). (noun) hinged or detachable flat section (as of a table or door). (verb) turn over pages. (verb) produce leaves, of plants.
lief: NA
leaf: l·IY·f
lief: l·IY·f
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)