radical / radicle 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. 👇
radical: (noun) a person who has radical ideas or opinions. (noun) (mathematics) a quantity expressed as the root of another quantity. (noun) a character conveying the lexical meaning of a logogram. (adjective) arising from or going to the root or source. (adjective) of or relating to or constituting a linguistic root. (adjective) especially of leaves; located at the base of a plant or stem; especially arising directly from the root or rootstock or a root-like stem.
radicle: (noun) (anatomy) a small structure resembling a rootlet (such as a fibril of a nerve).
radical: r·AE·d·ah·k·ah·l
radicle: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)