The words tighter, titer sound the same but have different meanings and spellings. Why do tighter, titer sound the same even though they are completely different words?
The answer is simple: tighter, titer are homophones of the English language.
comparative form of tight: more tight
comparative form of tight: more tight
A ribbon or string used to draw clothes closer.
Concentration of a substance in solution or the strength of such a substance determined by titration.
The minimum volume needed to cause a particular result in titration.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, from The American Heritage® Dictionary of the English Language, 4th Edition 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").