Final answer:
Commas with introductory elements are used to separate words, phrases, or clauses at the start of a sentence from the main part. Nonessential information, which does not change the sentence's basic meaning, is also set off by commas. These rules improve clarity and reader comprehension in sentences.
Step-by-step explanation:
In English grammar, commas serve to separate elements within a sentence to clarify meaning. An important rule involves the use of commas with introductory elements. An introductory element can be a word, phrase, or clause that provides context or background information at the beginning of a sentence and is usually followed by a comma to signal the start of the main part of the sentence. For example:
- After class is over, we should get lunch and review our notes.
- Shuffling his feet nervously, he waited for the train.
- However, the circumstances have not changed.
Commas are also used to separate nonessential information, which is information that can be removed without altering the basic meaning of the sentence. Conversely, essential information, which is crucial to the sentence's meaning, should not be separated by commas. For instance:
The labs, which are outdated, no longer meet the needs of the teachers and students. Here, the phrase 'which are outdated' is nonessential and is properly set off by commas.
These punctuation guidelines help readers understand the separation of ideas and the emphasis on certain parts of the sentence in an analytical report and other forms of writing.