Correct spelling, explanation: the correct form is fifth. English words that denote order and contain the number five are consistently spelled with f-i-f-t-h. This follows the general rule for forming ordinal numbers (fourth, fifth, sixth, etc.). Fifth includes the fth sound at the end, which aligns with how ordinal numbers are typically pronounced. The spelling fith would not accurately represent this sound. Using fifth ensures that your writing adheres to conventional spelling rules and is understood correctly by readers.

Definition of fifth:
Number, constituting number five in a sequence; 5th
She won the fifth race in the championship series, securing her place in the finals.
On the fifth day of our vacation, we visited a beautiful national park and went hiking.

Collocations with fifth:
Some of the most commonly used collocations include:
1. Fifth Avenue: a major thoroughfare in Manhattan, New York City.
The parade marched down Fifth Avenue with colorful floats and music.
2. Fifth grade: the grade level in school that typically includes students aged 10–11.
My brother is in the fifth grade and loves his science class.
3. Fifth wheel: an extra person or thing that is unnecessary or superfluous.
I felt like a fifth wheel at the party since I didn’t know anyone there.
4. Fifth Amendment: a part of the United States Constitution that protects individuals from self-incrimination and guarantees due process.
He invoked his Fifth Amendment rights during the court proceedings.

Incorrect spelling, explanation: you can’t spell fifth as fith because it deviates from standard English spelling conventions and pronunciation rules. The word fifth is pronounced /fɪfθ/ or /fɪθ/. The fth combination accurately represents the sound made when pronouncing the word, especially the ending consonant cluster /fθ/. Spelling it as fith omits the -f sound before the th, which changes the phonetic accuracy of the word. The word fifth originates from Old English fīfta, which has evolved into the current spelling. This historical lineage influences its correct spelling.