Today I took an English Writing class, and my professor assigned sentence correcting practice exercises.

Five components of defective parts have been identified, one of which is severely damaged.

My professor corrected this sentence by replacing the comma (,) with semicolon (;).

Then I discussed the grammar plausibility of the uncorrected usage, and then he said the comma is not strictly correct, but the semicolon is for formal usage.

Do native English speakers have this usage?

  • 2
    The normal ways to offset a parenthetical are with commas, dashes, brackets or zero punctuation. Commas and dashes occur at the end/s of the parenthetical, and are paired for medial parentheticals, while terminal/initial punctuation replaces one for terminal/initial parentheticals. Semicolons are most unusual, many would say unacceptable. Commented Feb 29 at 15:22
  • 1
    The semicolon harms the meaning the sentence. But returning to argue with the professor will harm your grade. Commented Feb 29 at 15:24
  • 2
    Does this answer your question? Usage of brackets/parentheses (etc). << Five components of defective parts have been identified, one of which is severely damaged. >> = << Five components of defective parts, one of which is severely damaged, have been identified. >> The parenthetical may be terminal or medial. Commented Feb 29 at 15:27

1 Answer 1


Semicolons are used (primarily) to join independent clauses. The sentence in question consists of one independent clause (“Five . . .”) and one relative clause (“one of which . . .”). Relative clauses are subordinate and cannot stand on their own. In order words, “One of which is severely damaged” could not function as its own sentence; the relative pronoun needs some antecedent within the same sentence. Thus, the usage of a semicolon here is incorrect, and the comma is appropriate, even in formal registers.

Not the answer you're looking for? Browse other questions tagged or ask your own question.