Anyone who has suffered the utter horror of a gritty mouthful of undissolved sugar from the bottom of a glass of iced tea* will find it fitting that the Sanskrit word from which sugar is derived, śarkarā, also means “gravel.” That same Sanskrit word also led to two homophones whose spellings can be confused by even the most diligent proofreaders: saccharine and saccharin.
The word saccharine has been in the English language for over 300 years. Historically, it was an adjective that described something that was related to, resembled (in flavor), or produced sugar.
Saccharine had no homophones until the late 1870s, when Constantin Falhberg, while working on something completely different, accidentally discovered the saccharine properties of benzoic sulfamide, which is several hundred times sweeter than sugar. Benzoic sulfamide was given the e-less name saccharin and sold as a sugar substitute. (It was also sold in various forms as a cure-all for everything from headaches to obesity.)
Sugar shortages during World War I led to more widespread use of saccharin (also known today as “the pink packets”) among the general population. Whether through miscalculations in recipe substitutions or mere curiosity, people quickly learned one of the truths about saccharin: Adding too much of it not only made foods too sweet but left a bitter or metallic aftertaste.
Since that time, the meaning of the adjective saccharine has shifted to become more descriptive of its homophone saccharin. These days, saccharine more often than not is used to describe something that isn't just sugary, but sickeningly sweet or cloying, or (metaphorically) ingratiating or overly sentimental.
Automatic spell-checkers won't help you decide whether the word on your screen should end with an e. Here's a mnemonic that might help you remember the difference: The noun saccharin ends with an n, and so does noun; similarly, adjective and the adjective saccharine both end with an e.
Pretty sweet, huh?
*This is intentional hyperbole meant for comedic effect. Please don't write letters.