The words florescence, fluorescence, fluorescents sound the same but have different meanings and spellings. Why do florescence, fluorescence, fluorescents sound the same even though they are completely different words?
The answer is simple: florescence, fluorescence, fluorescents are homophones of the English language.
A condition, time, or period of flowering. See Synonyms at bloom1.
The emission of electromagnetic radiation, especially of visible light, stimulated in a substance by the absorption of incident radiation and persisting only as long as the stimulating radiation is continued.
The property of emitting such radiation.
The radiation so emitted.
Plural form of fluorescent.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").